Hello Vivian,

Actually, it's not as challenging as you might think. We contract them frequently. A good installer should know how to make one to your specified size. There are plenty of You Tube videos and instruction on DIY websites. Take a look at a few Houzz ideas for inspiration; if they can do it you can, too:





Best of luck with your bath renovation and please let us know if we can be of additional assistance,
Elizabeth Cabell, ASID, CID
Cabell Design Studio

You can have a base made from waterproofing membrane and tile to fit exactly for less momey than a custom base. Schluter makes all the products you need to this DIY