I apologize for the lack of some crucial photos, as once the process is started and the gloves are on, the epoxy usually gets everywhere so I try to limit my camera's exposure to it.
Step 1: Tools and Materials
Epoxy resin (marine-grade)
Fiberglass tape (11.1 Oz best for structural, bi-directional not necessary)
Most of these materials can be purchased at a marine supply store.
Step 2: Cut it out
If your pieces are joined at odd angles, you can choose to cut the pieces out at an angle, or just use a file to shape it later.
Step 3: Drill Some Holes
Depending on the amount of curve in the pieces you're stitching, drill holes that will accommodate your Zip-ties anywhere from 3" apart to 6" apart, about 1/4" to 1/2" in from one of the piece's edges to be joined. This definitely does not have to be exact.
Now mock up the two edges to be joined, the one with holes in it and the one without. Try to clamp it as best you can for at least a few feet, especially if it's curved. Then, drill holes in the untouched piece that line up with the holes in the other piece. Again, this really does not have to be exact.