I've been going to try this one for a while, just not enough time. Often they use "marine resin" (used in fiberglass repair with glass cloth on boats). They cover 2 boards with wax paper to prevent sticking and layer denim that has been coated with resin on both sides. Once they have enough layers they place it between the 2 wax paper covered boards and C-clamp it for pressure to squeeze out the excess resin. Some will layer different colors of denim for another look and some will make the denim strips long so that they can twist the denim before applying pressure for a "damascus look". Some folks use a press, but C-clamps will work. I saw a tutorial on this somewhere and thought that would be a good way to use my old Levi's.
So many great ideas, not enough time.
PM sent.