Step 1: Create Mounting Brackets
Once you have a good sized chunk melted, attach the blob to the end of your smooth rod. Its not important at this stage to shape it, simply attach it. Now put the rod to the side for a couple minutes to cool, and start melting more plastic for the next rod or other end.
After a few minutes, the plastic will cool and be easy to work with, yet wont burn your fingers. Shape it so there are 2 tabs, one on each side. These will be where you drill through to attach it to the frame. Once it cools even more, lay it on something flat and hard and flatten the bottom so it will set well on the frame. After it cools completely, rotate one of the brackets so you can get them both aligned perfectly.
Step 2: Mount Rods on Frame
Now you will want to align the rods. It is very important that they are parallel to each other, and square with the frame. Measure multiple times. We also found that having a square was very useful, as we could set it to the width between the rods and then move to the other end and push them together or apart until they were perfect. You could easily do the same thing with a piece of wood. Once you have the rods aligned, you will want to fully secure them by putting screws in each hole. You will have to do this for both linear stages.
Step 3: Mount Platform on Rods
This part was really easy. Just mark where the rods pass under the board, and then heat up some plastic. Put four blobs of plastic on the board, and then take it to the stage. Line it up and press it on the rails. Make sure it is level and square. Its a lot easier to do it now, rather than reheating and remolding later. Now wait for the plastic to cool and then take your stage off the rails. Slide it around to make sure it works. If you did everything correctly it should slide pretty easily and you'll probably be jumping up and down happily.
Later you will want to add some sort of lubrication to the rods, but for now you have 2 working linear stages!!