Gina, I dug a trench 16" deep and stood 4"x8"x16" cement blocks into it, making an almost 16" deep foundation with them.
I then made a 2 by 4 base, using pressure treated lumber, directly on top of the blocks. The wood doesn't rot as quickly, because it's up ever so slightly off the ground.
The netting I used in previous years got chewed through by those little beasts, but the thicker stuff really holds up.
Your friend might want to use chicken wire all around the base, and drape regular bird netting over the top, to prevent the aerial attacks.
I didn't cement the blocks into place. I back filled the trench with small rocks and soil, and watered it really well, basically packing the soil into something impenetrable.
It was a lot of work, but I hate that these freeloaders are all over the place, taking two bites out of everything they see, and setting up a permanent summer home.
I gave them their own patch, about 10'x20', away from my patch, but they don't understand the concept.
The cement blocks are cheap, about $1.30 a piece.
I may do a vertical strawberry setup next year though, I still get a lot of damage from slugs. Almost half of the fruit gets damaged, and I don't go where the escargot!
There are some videos on youtube with ideas for vertical strawberry growing.