Fake Boulders- how to make rocks

I would like to add several bolders around my pond and waterfall. Does anyone here have experience making them? I like the idea of covering forms with spray foam then finishing, but I do not know where to get a large amount of the spray foam. The small cans from HD or Lowes would be costly.

How To Make Artificial Rock Panels - WaterfallNow custom water

How to Make Faux Rocks : 9 Steps (with Pictures) - Instructables

Eddie Medelez (@eddie_medelez) / X

Nové solisko pre zver a lesný čaj

DIY Landscape Boulders How to make fake rocks

Fake Rock Key Holder with EasySculpt - Resin Crafts Blog

21 FAUX ROCKS ideas faux rock, fake rock, landscaping with rocks

190 Best Sement ideas concrete diy, concrete crafts, concrete projects

Faux rock Faux rock, Waterfalls backyard, Fake rock

Eddie Medelez (@eddie_medelez) / X

57 Art of cement structures ideas faux rock, fake rock, artificial rocks

Landscape Rocks & Pebbles for sale in Detroit, Michigan