Heat the oven to 425°F and press the ground beef into a 9-by-13-inch rectangle on a rimmed sheet pan.
Season with salt, black pepper and garlic powder and bake for 10 to 12 minutes until the center reaches 160°F.
Drain the beef slab and lower the oven to 350°F.
Split the connected rolls, spread ketchup and mustard over the bottom, and add the beef slab and American cheese.
Replace the top slab, brush with butter and bake for 8 minutes until the cheese melts.
Lift the tops, add the drained pickles, close and cut into 12 sliders.