On many distros, getting multilib support is very straight forward. There exists a guide that can act as a replacement for LFS: compiling and configuring a system that can boot, run, and compile software; and also have that same ability with 32-bit. It acts to form the basis that will allow you to follow any of the instructions laid out in the Steam and Wine chapters.
Such a guide is maintained by Thomas Trepl at https://www.linuxfromscratch.org/~thomas/multilib/. It is very comprehensive and also covers how to get x32-bit support, a format that can run 64-bit code with 32-bit registers. That format is unnecessary. Most applications that are covered here either don't: support it, require it, or is simply not necessary to compile for any sort of interest. Therefore, any mention of x32-bit, x32, mx32, and x32-bit instructions can be skipped. Most users will not need it and the extra support in compilers and libraries on the system will be useless, taking up disk space.
The same principles of compiling for 32-bit in that book will also apply to this book as well. If you haven't already, read Important Information to check what basic principles still apply in this book when targeting 32-bit.