The most common mistakes are surprisingly consistent. The first is soggy bread, caused by putting wet fillings against untoasted bread; toasting and sealing the bread with sauce or cheese prevents it. The second is a lack of acidity, which is why many rich sandwiches taste flat — adding pickles, mustard or pickled onion fixes it instantly. The third is overloading, where too many fillings make the sandwich impossible to bite and blur the flavours; fewer, better fillings are the answer. A quieter mistake is under-seasoning the vegetables, which leaves the sandwich tasting dull. Finally, serving a sandwich too long after it is built lets the bread soften and warmth fade. Avoid these five and almost any sandwich improves dramatically.

Focus on a short checklist that targets the usual failure points. Start with the bread: choose fresh bread that suits the filling and toast it, which prevents sogginess and adds crunch. Build in acidity with pickles, mustard or pickled onions so rich ingredients have something to cut against. Resist overloading — pick one or two quality hero fillings and a few purposeful supporting layers rather than piling everything in. Season your vegetables lightly, because unseasoned produce is a common cause of blandness. Keep the wettest ingredients toward the middle so they do not soak the bread, and, crucially, eat the sandwich fresh rather than letting it sit. Run through those steps each time and your sandwiches will be consistently good.