it looked like they just used resin and fiberglass tape. Keep in mind they were bonding to a clean fresh surface. West Systems makes an epoxy bonding filler which comes in a calking gun tube. I think I would use that on the surface between the wood and wall, then resin and fiberglass tape on both sides of the wood. On my next floor replacement I plan on using the West System filler to help fill voids when attaching the floor to the camper walls.
One note about theSix10 epoxy adhesive. The two parts of the epoxy is mixed in the tip. Unless you plan on using it all at once you should order extra tips. If you remove the tip the tube will squirt out both parts of the expoxy mixture and then you can then mix it with a putty knife or plastic tool. You can only use a tip once.