Prepare spaghetti noodles and sauce as you wish, lazy spaghetti on stovetop or in pressure cooker as linked above. Can add frozen meatballs when cooking to thaw and become tender if you like or leave those out.
You can toast buns with a brush of melted butter opened and placed inside a pan on the stovetop until browned.
Use tongs to fill each bun with spaghetti. If you would like to add cheese, baked until melted put on baking sheet opened with parmesan cheese sprinkled on the top of each one.
Put into preheated oven at 400 degrees for 5 minutes until melted, then serve.