I used dowels to attach my Yost coaming to the base ring:
- Pick up some dowels. I went with 1/4" hardwood, if I remember right.
- Get some wood glue. Since I don't expect the coaming to be continuously submerged (and if it is, I'll be more concerned with trying to grow gills than whether the glue is going to hold), I used Elmer's Carpenter glue. Epoxy should be fine, too.
- Use a few clamps to secure the coaming and ring together and make sure nothing moves.
- Drill a hole through the coaming and the base ring. Use the same diameter bit as the dowels. Wiggle the bit a little to get a little more clearance when inserting the dowels.
- Test the fit of the hole by inserting the dowel into the hole. Remove it.
- Measure and cut the dowel to match the thickness of the base plate and ring.
- Drip a bit of glue into the hole, and smear a bit around the pin (what I'm gonna call the cut dowel).
- Insert the pin.
- Keep it clamped until the glue cures/dries.
- Repeat every 6" or so around the coaming.
- I sealed the ends of the pins when I painted the coaming and the rest of the boat. If you're not painting, you'll need to find some other way to seal the ends of the dowels. Seein' as the end grain of the dowel might suck in enough water to swell and cause problems, I'd feel better about sealing 'em.

When you want to remove the coaming (when you're reskinning, for example), simply drill out the pins. Simple.