I've found this carry system very user friendly. Strap the paddle onto the board, and carry board by the paddle. It gives you good control when carrying the board in windier conditions. Also gives you good control when going up and down steps at the coast. Easy to swap the board to the other arm, without putting the board down....

It also frees up your other hand.

It would be easy to add to any board. Just get two lease plugs installed. A bit of string and velcro to finish off... or order from Tropical Blends. Bodyboarding Flipper Savers are similar, but effectively longer. I leave them on the board. If you make some up, make sure there's nothing to catch your toe on.... could get ugly otherwise....

(first picture is not my photo - from Kayak Shop Mona Vale)