Put steak, 3 or 4 chipotle peppers, 3 to 4 Tbsp. adobo sauce, green onion, half the cilantro, lime juice, salsa, and salt and pepper into your slow cooker. Cook on high for 4 to 5 hours, flipping it about every hour.
Shred the meat.
In a skillet on medium high, add a tortilla to the pan. Top one side with cheese, meat, red bell, cilantro, and a little more cheese. Fold in half and cook until tortilla is golden brown on each side and cheese is all nice and melty.
Slice it with a pizza cutter and serve immediately.