what dimensions for a 12” sb cr77 subwoofer?

if you can have the driver measured, get complete specs, designing a good box will be fairly straight forward

Drivers are designed for either ported enclosures or sealed enclosures. You should start by finding out which driver you have.

To make best use of the 'book about building speakers', you will need the TS parameters of the driver in question.

Online caclulators or quick downloads will guide you to proper dimensions.

With good woodworking skills, the TS parameters and some experience, you can get remarkable performance from a DIY sub.

The plate amp makes a difference here, so don't skimp.

Parts Express or Madisound may help with driver parameters. They maintain a database.

If it were that easy, everyone would make their own. Companies put years of R & D into developing these type of things. Theres no way that you will be able to build anything that even comes close to a professional design. Something tells me you already suspect this. If you just want box dimensions, look at some subs with 12' drivers in them and go by that.