Use leftovers from Roasted Pork Loin with Black-Bean and Sweet-Potato Salad to make this super sandwich.
In a large skillet over medium heat, cook bacon until crispy, turning once, 6 to 10 minutes; transfer to a paper-towel-lined plate.
In a small bowl, mix mayonnaise and scallions; season with salt and pepper.
Place bread on a work surface; spread one side of each slice with mayonnaise mixture. Layer 4 slices with pork and avocado; layer 4 other slices with sprouts, bacon, and cheese. To assemble sandwiches, stack layers; top each with 1 remaining slice. Spear sandwiches with toothpicks, then halve with a serrated knife. Serve with dill pickle spears, if desired.