Gather a few supplies:
22" x 30" watercolor paper, 140 lb hotpress, Fabriano Artistico from Dick Blick's works fine
good metal ruler
polyester thread approx. 3x the length of the journal spine
Tear the sheet into 10" strips. Fold one sheet in half. The other two sheets will be folded at 8" and 16".
Fold left to right. Fold over that extra 6". Do this to both sheets, then nestle them oppositely to each other. The sheet you've folded in half will have a couple of extra inches of paper, fold those in so they are even with the other pages.
Mark the holes in from 1 1/2" at the top and bottom of the spine and then mark a hole in the middle. Sew from the center hole inside to outside center, go up through the top hole in the spine, carry your thread all the way over the inside and go down through the bottom hole on the spine. Go back up the center hole and tie strings in the center. Be sure to secure the long thread with the knot from the threads coming up from the center.
These are my notes and supply list I've had written on a post it note for quite a while. When I figure out where I was when I took the notes, I'll will give credit where credit is due. (Oh, and my notes state "don't use Arches paper - don't know why - too stiff maybe.) I would take a picture, but all I have is white paper, haven't threaded the journal or painted it yet.