Hi - I've used flatish rocks/slate piled up to about 6 inches high, pea gravel piled around, leaving the rest of the water area with a clear bottom. The water is 5 inches high.

Then I've squashed bits of moss into the 'joins' so to speak & this appears to be growing (hooray).

The toads seem to like it, and the moss helps them to climb up a level. Its easy to cope with too.

Hope this helps.