One of the cautions I received when I proposed making a sloping beach
in my mini pond was to not use sand as it would all end up in the
bottom of the pond.

OK- so then I saw an article online that proposed mortaring a band of
round stones across the slope to hold the beach from slipping lower.
I'm in NY so I'm always conscious of frost heave and don't like the
idea of sharp broken edges of mortar on my pond liner. [it will be 45
mil EPDM]

I've been looking unsuccessfully for something online that discusses
doing the same thing with silicone or some flexible cement.

I want a few feet [about 15-20 square feet] of stone bottom, up to
about 6" deep for birds & dogs to splash about in. What's the
best way to accomplish this?

Thanks,
Jim