The Y-axis cutting guide, including the aluminum angle brackets. The angle brackets are the same throughout this project, both for the linear bearings and for the mating surface. With the 'front' and 'back' parts, you may need to 'futz' with their length in order to secure a good, solid fit against the Y-axis frame. At this point, I have not included instructions for where/how to mount the nut that accepts the drive screw. I'll get to that later.
Notice the detail when cutting the front. I set my table saw for 45 degrees (you can also use a router with a 45 degree bit and a guide bearing). I left small flat ends on each side (detail inside circle), not a sharp point. This is to allow a good, straight surface to rest against the fence of the table saw (or the bearing of the router bit).
Here is the entire assembly. Again, you may need to 'play' with the length of the front and back to secure a good, solid fit of the bearings against the Y-axis rail.
Now you can trial fit the Z-Axis assembly onto the "front" of the Y-axis. Again, some experimentation with the width of the Z-Axis to fit snug.