To make the rib spacers, I use two of the "scrap" pieces left over from building the lute rib form. It's very simple to just take a hand saw and saw a groove on the outside edge of the scrap form piece to accept the rib spacer to be bent. Here you see the two leftover pieces from the lute form, with spacers taped in the outside groove while they dry. For some spacers such as maple, I have been able to simply soak the spacers and bend and tape them into the form as shown. Other materials, such as walnut seen below require bending on the iron to avoid cracking.Here are maple spacers drying.
Bending on the iron may be required for some materials - but it is easy...
Here is a spacer just removed from "drying" and ready to be installed.
Just use tape to hold everything together while the glue dries - no mold required.
Go here to see how to assemble the ribs without using a mold.