Simple spool holder I designed for use in IKEA 365 Container, 10.6L variant. The print fits snug in the bottom of the container, no glue or tape needed. The angled surfaces that hold the spools have ribs to keep the spools from moving around too much.
Optional humidity meter can be attached. This is the simple meter that can be purchased everywhere (mounting hole 26mm*46mm).
Maximum spool size: about 20cm in diameter, 8cm thick.