To keep buns from getting soggy, create a buffer between wet ingredients and the bread. Lightly toasting or grilling the cut sides forms a moisture-resistant barrier. Spread a thin layer of fat—butter, mayo, or aioli—on the cut side before toasting to improve flavor and resistance to sogginess.
Place wetter toppings (tomato, pickles, sauces) away from the bottom bun or layer lettuce between the patty and bun to act as a moisture shield. Assemble burgers right before serving to minimize standing time, and if you must prep ahead, keep wet components separate until ready to eat.
These small steps preserve bun structure and make the burger easier and cleaner to eat.