Spool clamps are relatively inexpensive to buy, but in order for them to be useful in lutherie, you need a whole pile of them, and then the cost builds up quickly. On the other hand , they are one of the easiest tools you can make yourself, and for a lot less than buying. (Especially here in Canada, where the shipping from the US, plus customs duty and fees add up quickly)
As usual, there are many resources available to show you how to do this, I like this one, because he show you some easy jigs he used to make the process less tedious; make your own spool clamps | RATTLECAN GUITAR RESTORATIONS by James O’Rear .2