All manufacturing technology, I think, is clear from the photos.
The inclined plane can be made of cardboard. For young children, you need to either take a wide inclined plane, or make side walls at an inclined plane. Otherwise, the toy will fall abroad all the time.
But for office entertainment, the usual wooden ruler is suitable. On a plastic ruler the toy will slip and somersaults will not work.
The task is simple - by adjusting the slope of the ruler to reach the finish line and prevent the toy from falling overboard.
The second varinat tumbled:
This fun toy will appeal to kids. She slowly descends along an inclined plane, while doing somersaults (before each somersault - a short stop).
Paper somersault. She glues on a wooden disc. (Styrofoam can be used as a blank.)
Take a block of 25 by 25 by 75 millimeters, round off the edges, as shown in the figure, clean the blank with sandpaper. Having put a layer of paper on the blank, glue the second one on top, then again and again so that a wide paper "rim" with a thickness of about 2 millimeters is formed. Remove the disc, glue two discs (from cardboard) to the rim. Insert a metal ball with a diameter of about 20 millimeters in advance. Fix the sides properly so that they do not fall off (you can use strips of paper). It remains to put the somersault on an inclined plane.