On the Franklin River recently we had some interesting portages.
The easiest way was to strap the pack on the bow in such a way so that we could pick the boat up and walk with it inflated on our backpacks.
This video shows how to attach the pack to the boat in a simple, convenient and secure way using straps. The straps work for other purposes too when not boating or portaging, like anchoring a pyramid tent or holding a flapping sole to its upper on an unruly shoe.