Slice the chicken breasts in half lengthwise (place your hand on the chicken breast, then carefully cut horizontally), then cut each portion in half.
Lay a piece of wax paper on top and pound them gently with a mallet until they are even in thickness.
Season each side with sea salt, freshly cracked pepper, and garlic powder, to taste.
Coat a grill pan with olive oil and heat over medium-high heat. Once the pan is hot, add the chicken and cook for a few minutes until they are golden brown. Flip over and cook for 2 minutes, or until cooked through.
Remove from the pan and set on a plate with a foil tent placed loosely on top.
Place the slider buns on the grill pan and let them toast for a few minutes, then remove from the pan and spread some mayonnaise on the bun halves.
Place a piece of chicken on the bottom bun, followed by avocado, tomato, onion, lettuce, and top bun. Serve immediately and enjoy.