Gruul Sligh applies early pressure with one-drop threats like Jackal Pup, Mogg Fanatic, and Grim Lavamancer, backed by cheap burn spells that can pick off your mana creatures or close out the game. Your primary goal is to combo off as fast as possible through Hermit Druid or Survival of the Fittest before their damage adds up, so protecting your Birds of Paradise and Wall of Roots is critical. Pyroclasm is your most impactful sideboard card, as a single copy can wipe their entire board of x/1s and x/2s, buying the time needed to assemble the Hermit Druid line. Ghitu Slinger and Gorilla Shaman come in via Survival to answer Grim Lavamancer (which hoses your graveyard-based combo) and any equipment or artifacts they might bring in from the board. Be wary of their graveyard hate in Tormod's Crypt and Pyroblast post-board, but your speed and redundancy through Survival should still be favored to goldfish the win before their disruption lines up.