GGACR/Slayer/Starter

Key Moves

6KGuardHigh/AirStartup21Recovery1+3 after landingAdvantage+5 is one of Slayer's overheads that serves as an Oki tool and can be gatling into to open people up.
5KGuardMidStartup6Recovery8Advantage+1 is Slayer's best midrange poke for neutral.
c.SGuardMidStartup7Recovery10Advantage0 is great for combos, frametraps, and throw OSinputting a throw as 6H+S will cause c.S to come out instead if the opponent takes an action that makes them throw invulnerable, such as backdashing or jumping.
2PGuardMidStartup4Recovery5Advantage+3 is Slayer's fastest normal, has minimal recovery, incredible air hit untech and is great for scrambling hit confirms or Abare An attack during the opponent's pressure, intended to interrupt it..
2KGuardLowStartup6Recovery11Advantage-1 is a quick low that is used for mixups, poking and blockstrings.
2HGuardLowStartup13Recovery22Advantage-5 is a lower body invulnerable, low hitting poke with good range that is really good at beating low profile moves where 5K would whiff.
Route into 2DGuardLowStartup7Recovery12Advantage-8 to secure knockdowns on most stray grounded hits.
Mappa Hunch (236P & 236K)GuardMidStartup14Recovery16Advantage-3 is an essential harassment tool with a bad hitbox and subpar reward on hit.
Dandy Step (214P & 214K)GuardStartupRecoveryTotal 30Advantage- is a sway like move that can be used defensively and offensively and cancels into PilebunkerGuardMidStartup3Recovery33Advantage-17 (Dandy Step > P), Crosswise HeelGuardMidStartup6Recovery16+5 after landingAdvantage-14 (Dandy Step > K), Under PressureGuardMidStartup5Recovery15Advantage-3 (Dandy Step > S) or It's LateGuardHighStartup18Recovery9Advantage+4 (Dandy Step > H). The force break version of this move, FB Dandy Step (214D)GuardStartupRecoveryTotal 30Advantage-, grants a ton of strike invulnerability.
Dandy Step (214S & 214H)GuardStartupRecoveryTotal 30Advantage- move forward and can cross up at the right spacing and cancels into the same follow ups.
Big Bang Upper (236D)GuardMidStartup10Recovery35Advantage-22 aka BBU, is mostly a punish tool with it's high invulnerability and combo filler that can take your combos corner to corner.
Anti Air
5PGuardMidStartup5Recovery4Advantage+2 is a good panic anti-air. It’s fast, disjointed, mashable and hits pretty high in front of Slayer's face.
6PGuardMidStartup18Recovery14Advantage-1 has really good upper body invulnerability allowing it to act as a good counter to low IAD attempts and counter pokes.
2SGuardMidStartup8Recovery15Advantage-7 is a bit slower than 5P, but it has a really good hitbox to beat out quite a bit of jump ins and catches above and slightly in front of Slayer.
Crosswise HeelGuardMidStartup6Recovery16+5 after landingAdvantage-14 (Dandy Step > K) is your go to anti-air while in dandy step and has a good amount of upper body invulnerability however it is slow to start-up.

Combos

Slayer wants to route into knockdownsExamples:2D/j.D/It's Late/Pilebunker for Okizeme From Japanese "起き攻め". Attacking an opponent about to wake up after they were knocked down, usually with meaty attacks or mix-ups. while dealing as much damage as possible

2K > 2S/2H > 2D is a very basic Knockdown combo.
6K/5K/2P > 2K > 2H > 2D are slightly harder combos that deal more damage and still results in a knockdown.
6K > 5K/2P > 2K > 2D overhead starter that leads to a knockdown.
StarterExamples: Air to air j.K/j.P, ground to air 5P/2S, Crosswise Heel, etc into > j.K > j.2K > j.K > jump cancel > j.K > j.2K > j.D is Slayers's typical air combo structure.
2H > 236D > 2D > c.S > j.K > j.2K > j.K > jump cancel > j.K > j.2K > j.D.
You can omit the jump cancel in longer combos and end on j.K > j.2K > j.D for a knockdown which is especially relevant in routes involving 236D.
Combo Starters
5KGuardMidStartup6Recovery8Advantage+1 is your neutral poke that can link into 2K that leads to 2D.
6KGuardHigh/AirStartup21Recovery1+3 after landingAdvantage+5 can be gatling'd into during pressure and open up your opponent who is just blocking low.
2KGuardLowStartup6Recovery11Advantage-1 is part of your high-low mix together with 6K and It's Late (Dandy Step > H.
2PGuardMidStartup4Recovery5Advantage+3 is your fastest mash option that can link into 2K to get you a knockdown.
It's LateGuardHighStartup18Recovery9Advantage+4 (Dandy Step > H) (also referred to as raw It's Late) is throw invulnerable on start-up, hits overhead, is one of your main tools on Oki and can link into 5K/2K/2P

Blockstrings & Pressure

Getting within 5K range gets the party started for Slayer letting you special cancel,IAD or frame trap

Some examples:

5K, 5K
5K, 5K IAD
2P, 5K S dandy
2P, 5K forward dash throw
5K, 5K, 5K
5K, 2K, 5K
2P, 5K, 5K
2P, 5K, 2K
2P, 5K, 6K
2P, 5K, 6H -- Good to try and catch back dashes or up backs but works best when you've conditioned them to not mash here
2P, walk up throw
2P, 6P -- frame trap once you've established throw, 2p gatlings into 6p
2P, 2P, FDC Bite
2P, 2P, (2P), 6K/2H -- Max range hitting 2P into 6K and 2H can let you space out 6K and 2H to CH fast hitting lows like JO 2H, KY 2D, SO 2D
2P, 2P, 6H

Both 5K and 6H are special and jump cancellable so you can try and extend/rebuy pressure with any string ending in those buttons. Of course, this list isn't exhaustive but provides a good baseline to work from.

Spending Meter

FB Dandy Step (214D)GuardStartupRecoveryTotal 30Advantage- allows you to steal your turn at any moment and FB dandy > PilebunkerGuardMidStartup3Recovery33Advantage-17 (Dandy Step > P) is really good at interrupting pressure though it is very minus on block.
Combining FB dandy and FB PilebunkerGuardMidStartup3Recovery31Advantage-3 (Dandy Step > D) makes it much harder to punish being -3.
Using FB dandy > Under PressureGuardMidStartup5Recovery15Advantage-3 (Dandy Step > S) let's you re-buy pressure after being FD'd out and is relativley safe at -3.
Big Bang Upper (236D)GuardMidStartup10Recovery35Advantage-22 can be combo'd into from 2H and has great corner carry.
Chokkagata (j.214214S)GuardMid [All]Startup7+2Recovery20 after landingAdvantage- done early in a combo can do great damage and even let you continue the combo if it wallbounces.
Dead on Time (632146S)GuardAllStartup7+1Recovery31+21 after landingAdvantage-43 can be combo'd into from various normals and is another great way to tack on unburstable damage.

What to do after a knockdown

From a

Slayer's goal after a knockdown is to start his high/low/throw game, get a knockdown, and do it all over again.

Do P Dandy Step (214P)GuardStartupRecoveryTotal 30Advantage- into It's LateGuardHighStartup18Recovery9Advantage+4 (Dandy Step > H). You can delay it a bit to beat throws for a juicy CH.
Do empty P Dandy Step (214P)GuardStartupRecoveryTotal 30Advantage- into 2K to score another 2D knockdown.
Do empty P Dandy Step (214P)GuardStartupRecoveryTotal 30Advantage- into throw.
Use S DandyGuardStartupRecoveryTotal 30Advantage- sometimes to throw people off and mixup reversal inputs. Use the same followups as P and K dandy step.
6KGuardHigh/AirStartup21Recovery1+3 after landingAdvantage+5/2KGuardLowStartup6Recovery11Advantage-1 is also a good option for oki due to it being an overhead, + on block and having low recovery. Doing it meaty allows you to recover and be safe from some reversals.
From a bad knockdownExamples:Throw/Pilebunker
Dash, c.SGuardMidStartup7Recovery10Advantage0/2K beats a lot of reversals, is hard to block and makes people want to throw you
5KGuardMidStartup6Recovery8Advantage+1/2K beats mashing on wakeup and also beats throw on wakeup
Dash throw, catches people trying to block your mix (loses to mashing)