The Impossible Dovetail Puzzle

This puzzle is not my idea it's just my version of it.The design side of things was pretty straight forward really in the free design software I use, have a look at the attached photos which shows you the basics of it, sketch a 60 x 60 square, extrude it to 30 mm and then sketch in 15 mm 45 degree in each corner, then join the corners and the corner to corner as in the photo, extrude the segments down to 15 mm and draft this to 15 mm creating the dovetail shape, turn this body into a component, create another 60 x 60 sketch using the extruded bottom face on the first component then turn this component off and extrude the sketch to 30 mm, create new body and convert into a component, using the combine tool as a cut, use the 2nd component as the target body and cut it with the first body, and tick keep the tool, we now have the impossible dovetail cube, the next job is to add the holes for the magnets etc.For this project you will need 1 x 6.3 mm steel ball and 1no 5mm diameter 2 mm thic