Sorry About the Covid part, hope you will be better soon…
You will have fun building it.
That is pretty much my bed size I used a CR10S Pro Bed witch is 310x320 , I had a bunch of linear rails left from a previus project 400mm long.
If you haven’t seen it yet here is my Build Thread also Dan @SupraGuy built his at the same size. Here is his Thread
If you need any of the files for that size printer let me know and I will share with you.
Good luck and let us know how it’s going.