My U-lock came with a bracket that mounts on the frame.

I don't always bring my cable but when I do I wrap it around the seatpost and use the Velcro that came with it to tie it up. I'm just copying what I've seen other riders do with their cables. When I first used my cable, I brought a separate lock for it, but then I learned the technique that includes putting one loop at one end of the cable through the U-lock.

For the OP, a lot of bike theft prevention articles/videos also advise, beyond locking methods, to personalize your bike with stickers, paint, etc. to make it less desirable.