In a medium bowl, combine the chopped spinach, scallions, garlic, ground turkey, and cumin. Sprinkle with salt and pepper, and use a fork to incorporate. Form into 12 1/2-inch-thick patties, being careful not to pack them too tightly.
Heat the oil in a large skillet over medium-high heat. Cook the patties (working in batches, if necessary) 5 minutes per side, until cooked through and golden brown. Avoid pressing them while cooking. Serve the sliders on buns, garnished with pickles, onion, and mayonnaise.