Making your own toasted sandwich is a great treat, but to be able to do it you need to have a sandwich toaster.
If you look at the breville sandwich toaster, you’ll see a typical model. What they do is they take a ready made sandwich and toast it to heat up the ingredients, giving you a hot meal rather than a cold one.
What you’ll find with a sandwich toaster is usually the option to toast two sandwiches at once. It will cut the sandwich in half, with the toasting process closing them off to an extent, which is what you want when you’re making a toasted cheese sandwich for instance.