CR 10 infinity mirror print bed

I used a combo laser + optic fiber from here: https://www.ellumiglow.com/laser-wire you could probably DIY something though. I used two plastic sheets from polycarbonate with a one way mirror adhesive film, and the stock glass bed.
As the full stack is higher than standard surface I used smaller bed springs.

The bed files are designed for a Creality Cr10 but you could probably scale it for other printers.

The two other files are used to clip everything together (use a bit of electrical tape to get a tight fit), and a support to place the laser emitter under the bed.