The different stages:
Design the top part that is going to move up and down.
Make 2 'L' shapes from plywood.
Glue and pin the 2 'L' shapes together to make a box.
Sand the box smooth and true.
Mark with a pencil where the hole are to go.
Drill the holes for the dowel to go through.
Cut the dowel to length.
Cut a cam out of plywood.
Cut a follower out of plywood.
Drill holes in the cam and the follower.
Cut out the shape to go on top, colour it and stick it on.
Tools used (scroll down):