Add Seasoning to the Middle of the Sandwich to Avoid Dampness
If you want to add some mayonnaise or mustard to your sandwich, but don’t like raw bread, try spreading these spices between the meats and / or cheeses.
Other ingredients that cause dampness, such as tomatoes, should also be in the middle. This careful approach to layering can not only help prevent raw sandwiches, but also keep them from falling apart when you try to bite off. (Also try creating a barrier with butter and dried mustard for the bread .)
The links to Kitchn and WonderHowTo below will help you refine your sandwich making skills even further.
The Best Ways to Pack Sandwiches | Kitchn via WonderHowTo