Customizable Tray - make Phone Holder or All-purpose Tray

This started off as a custom-fit tray to keep my iPhone from sliding off a lap desk, but I made it customizable so you can use it for all kinds of things -- even a box with a fitted lid by creating two trays with no cutaways the right sizes to fit snugly.

For a phone holder/tray:
- Measure your phone (object or inside dimensions you want)
- measurements set the inner dimensions of the tray
- Use the 'gap' parameter to adjust the fit

- The cutaways are optional and adjustable,