Cut the cucumber into thin slices (preferably with a mandolin, which gives thin, uniform slices).
Place them on a cutting board/plate in a single layer.
Sprinkle salt over them and let them sit for about 20 minutes - this pulls some of the liquid out of them, making them firmer.
Boil vinegar and sugar to make a brine - boil until the sugar has dissolved. Add spices to taste, e.g. peppercorns, allspice, and bay leaves.
Let the brine cool down to at least room temperature before using it.
Find a pickling jar and scald the inside with boiling water and possibly some preservative, ensuring it's free from bacteria.
Pour the brine into the jar.
Take a handful of cucumbers in your hand and squeeze them together to let excess liquid drain out. There's more than you might think since cucumbers are primarily made of water.
Put them in the jar with the brine and repeat with the rest of the cucumbers.
Stir them well and let them sit to marinate for at least 20 minutes, after which they're ready to serve. However, they get even better the next day.