Lead with Castform (Chilling Reign) to immediately spread 20 damage to all of your opponent's Pokemon with its Rainfall attack. Continue using Castform until it is knocked out, then if Alolan Sandslash GX is charged up using Aqua Patch or Melony with Energy Switch, use Spiky Storm GX to get 100 damage across the board. Then, try to draw more cards to enable the usage of Misty & Loreli, in order to use Spiky Storm GX again. If you're not able to, just knock out the active Pokemon with Frost Breath, or continue using Castform to continue the spread damage.