If you start with great bread then the carrier can become the focal point - Good olive oil or butter to griddle the bread to golden and toasty. If this is the case then stick to the 4 ingredient rule: a spread, a crunchy element (think pickles), something creamy and something meaty. The picture here is a classic pairing: smoked pork, goats milk brie, pickles and grainy mustard - the Bread is a Tuscan Boule griddle with olive oil. Don't be afraid to use salt and pepper - sandwiches are not exempt. And when ever possible, a balance of hot and cold temperatures add to the overall experience.
The next time you build a sandwich...take your time, respect the ingredients and build with intention.
Enjoy!