@garyj For mounting the rails I highly recommend these: Snapmaker 2.0 350 SBR16 Rail Holder by 3Dingo - Thingiverse as mentioned by @Waterboy in this thread: A350 Linear Guide Rail Mod - #13 by Waterboy
If you’re comfortable with and equipped for drilling and tapping, you can go that route, but these are a simple and effective solution that pretty much auto-align (at least within the tolerances that we can manage)