Digging animals don't understand wire. They try to dig at the base of the wall, hit something that can't be dug through, and get frustrated. They don't understand backing up to tunnel all the way from the edge of the wire.
Squirrels aren't so much of a problem as predators anyway.
Better to put the wire on the outside as an anti-dig skirt than to try to bury wire under the floor of the coop/run. Chickens are remarkable diggers and the wire is hard on their feet.
Wood chips, wood shavings, straw, pine straw, dry leaves ... pretty much any dry organic material can work as...
I wouldn't say great at building because it's my DH and sons that do most of the work, but I grew up in a handy family and am handy myself within the limits of my strength (the new, lighter-weight cordless tools help). So I know a lot about how building should be done even though my capabilities...
It can't look worse than my Splits Temporary Accomodations, which involve a dog crate, some scrap metal roofing, a piece of old tarp, and bungee cords.
https://www.backyardchickens.com/articles/mini-coop-or-integration-pen-from-a-large-dog-crate.76593/