The following I read about in an old magazine decades back, but it does work.
Take 2 thin, the thinner the better, cardboard tubes that closely fit inside each other. Cover the outer one with copper foil on the outside and the same for the inner tube.
Solder wires to them and you have a variable condenser. The longer the tubes, the more capacitance you have.
Now this is more of a "fun" project that a readily usable item, but just think of a neat 6' long tuning condenser!
. You can use foil also, but it's hard to solder to.
One method that was used to make fixed condensers was old photographic glass negative plates or cutting square window glass plates and alternate them with foil. Connect every other foil together, and you can make a fixed condenser that is capable of handling quite high voltages. This method was in some plans I saw for transmitters and Tesla coils.