The FUSE 8K instructions are almost finished. For now, there is the following video demonstrating how to separate and combine the bottom and top shell.

Separate bottom from top: Click to Play

Combine bottom and top: Click to Play

Check the Side button PCB
Some PCB versions have an extension which makes it impossible to add to the shell. The solution is to remove the green/yellow sticker with an Xacto knife or a pair of scissors.