I'm a complete novice, so I'm looking for some help

I saw a nice idea for the patio with a rigid liner surrounded by earth/sand,
then sleepers built round it.

However, I wanted our small rigid pond for somewhere else (maybe
semi-raised, as I can't dig much due to illness).

Could the raised sleeper idea be done with flexible liner ?
I'm talking about 4' 6'' x 3'

TIA

Peter