I had a go at making a stone wall on one of my 6 inch hedge bases. I followed an idea on YouTube which may not have been the best idea. I built three layers of lego up with one ‘bump’ depth and 6 inches long.
I then mixed up some PVA with some fine grain gravel (approx 3mm to 5mm grains) sufficient to fill the cavity and then spooned the mixture into the Lego form on the base and left the lot to dry.
Next day I started to dismantle the lego shell but found that the PCA hadn’t set so kept having to leave the most recent element exposed to dry as I went along. This took a fair few hours or mainly waiting around.
Eventually I managed to remove all of the Lego and left the wall to dry.
OK so the wall looks roughly OK, but given the amount of time wasted doing it hopefully I’ll come up with a more elegant solution for my next batch.