They've laid something called Cellotex (I think that's what its called. I keep referring to it as sellotape but I know that's not it!)
Then today they put down the metal rods over which they're gonna be pouring in the concrete.
They also dug a really big hole for the septic tank. If you'd have said to me a few years ago that I'd be excitedly taking photos of metal rods & septic tanks I'd have laughed in your face but who knew!!