the plants will still try to stand up even if you lay the pots on their side-- is this what you meant ? it could looke quite good--- different,

I once saw a vase shaped pot lying on it's side, and it had sort of burgandy coloured pansy's plantetd just inside the pot an some planted outside like it was wine spilled and running away from the pot

Intriguing idea but a pain to water I would think.

Just lay pot on top of soil in garden plant pansy's or plant of your choice, then water easy peasy lol

I could see ground hugging plants working, even perennials such as aubretia and some sedums