Here is a rough tutorial. The one I made above is cotton fabric with directionality. The one I make in this tutorial is felt – those tend to be very durable.

Step 1: Make a paper template to follow. I suggest you fold a paper in half, and use that to make your paper hexaflexagon. The folded paper will give you a better template. Here are some decent instructions for making the paper flexagon. Or here. Or a video here.

Step 2: Color your hexaflexagon. Then undo it, to reveal your template.

Step 3: Decide on the size you’d like (bigger is better, I think, certainly for your first one). The one I make in this tutorial uses triangles about 4 inches in height.

Step 4: Cut 18 congruent equilateral triangles out of your chosen fabric.

You will need 6 triangles of 3 colors.

I happened to cut a lot in this picture – far more than is needed for 1 hexaflexagon. 

Step 5: Arrange your fabric pieces according to your paper template. 

Step 6: Sew together each half of the hexaflexagon. I use a 1/4 inch seam. Be careful – I often end up ripping seams if I’m not paying attention to the directionality of the pieces. Particularly when adding the 3rd triangle in the line.

Step 7: Put both halves of the hexaflexagon right-sides together, and sew along each side. Leave the ends open.

You can pin it – you probably should, but I’m rarely that precise. Do try to keep the vertices relatively close together.

Step 8: Trim off any excess fabric to help when you turn the sleeve inside out.

Step 9: Cut triangles of peltex (fabric stabilizer) such that they fit inside the borders of each triangle. You will need 9 of them.

Step 10: Turn the sleeve inside out. 

Step 11: Fit the peltex inside the sleeve, and iron each triangle in – one by one.

Step 12: Fold your peltexed sleeve into a hexaflexagon.

Step 13: Sew two open ends together. You have to do this with the flexagon folded.  Full disclosure – I don’t have a perfect way of doing this yet. If you come up with something pretty – please let me know. I’ve tried by hand. I’ve tried by machine. I’ve decided to be fine with good enough. 

Step 14: Enjoy your flexagon! They’re often a bit stiff at first. Play with it for a while and it will settle into the hexagon shape more happily.