Sliders are small hamburgers, typically only about 2 inches (5 cm) across.
- Preheat oven to 250°F and a grill or grill pan to 350°F.
- Toast buns in hot oven. Set aside.
- Combine salt, pepper, garlic powder, and rosemary. Set aside.
- Combine chuck and sirloin, and place on a parchment-lined sheet pan. Cover with a sheet of plastic wrap and roll out until the meat fills the pan.
- Remove plastic and, using a pizza cutter or wheel, cut into 16 equal squares.
- Brush patties with olive oil and season on both sides with seasoning mixture.
- Cook patties on the preheated grill for 2–3 minutes per side.
- Spread buns with mayonnaise. Place a patty on top of a bun half and top with the other half. Serve warm.