Smørrebrød can basically be assembled freely. As the first step, slice the bread. Traditionally, it is most often made from dense, loaf-pan-baked, rectangular rye bread, but any kind of bread can work.
Butter the slices of bread thinly, and place a lettuce leaf on each one. Both steps can be skipped, but the butter adds a little extra flavor, while the lettuce gives the sandwich character—and also looks very good.
Pile the toppings onto the sandwich. Be generous: these days, smørrebrød is not so much a flat sandwich as one generously loaded with delicious things. Decorate it with tomato slices, English cucumber, lemon, parsley, sprouts, or other greens. To make smørrebrød, you can use any toppings you like, whatever you have at home, or whatever you feel like.