Does it have to be on the lake? Cal Black is just a few miles up the Colorado past the confluence (San Juan) On the south side. Probably the closest gas to the lake outside of Page. Hite is across the river and east on the north side. Both are 'airports' so although you didn't define 'easy' they probably fit the bill

From Cal black there are several off field strips within a 15 mile radius . Nokai dome is about 11 miles south, Zahn camp a few more. There is a strip on the Mesa between the Colorado and the San Juan just west of Zahns, but I haven't found anyone else who knows of it, so can't vouch for legality on that one, have coordinates if you're interested in exploring the issue tho... Nokai and Zahns are widely described on the net, try UBCP... I would call them very easy, but airplanes have been dinged on both. The strip on the Mesa has wide open approachs and is long, but narrow and soft...
Take care, Rob