As a scout leader of "idiots" i have leant the easiest knots

1) clove hitch - taught as a "P" and a "Q" - because they look like them!

2)Bowline-useful - although looks slightly complicated- method is simple

3)Figure of eight - very useful and very strong

4)Reef - easy-very useful in first aid

A lashing would probably be useful and i'd suggest-asquare lashing-started with a clove hitch - simple and effective

My opinions

Mark