It's very easy to do provided you've got a router, a drill, some plastic, a small length of stiff wire, sandpaper, q - cell, a small sheet of fibreglass and some resin (+ catalyst).
1. Drill holes in (but not through!) in your board where you want to start the rows.
2. Rout channels to the desired length, and sand around channels - area to apply glass.
3. Cut plastic to size.
4. Drill holes in plastic.
5. Mix up some resin and Q -cell to a paste.
6. Insert plastic with Q - cell paste filling gaps and bringing up to level.
7. Cut glass to size.
8. Mix up some resin, and paint onto glass over plastic.
9. Cut wire into small pieces and insert through wet glass into holes (this step makes holes easier to find once glass dries).
10. Once resin goes off(hard), remove wire with pliers and sand smooth.
This will leave you with a board ready to screw self-tapping screws into holes. Use screws that have a slightly larger diameter than drilled holes. Be sure to sand before glassing as resin will not stick to shiny surfaces.
This is the method that a professional will follow to insert straps to a surfboard.
I have followed this process on a number of boards and have never had a strap or "thread" pull out. This will not weaken your board anymore than having a professional insert boxes or than if you inserted single thread.
Good luck.
