This is how we made my son’s homemade Headless Halloween costume:
We bought an old coat from the local charity shop (an XL man’s coat). We filled an old hiking backpack with rags to bulk it out and put it on my son’s back. The coat was then placed over the backpack and buttoned up around my son’s neck. We filled out the arms of the coat with rolled-up towels, as they are flexible, and attached black washing-up gloves, filled with cotton wool, to the end of the arms.
We made the neck from my husband’s cereal bowl at work, covered it in papier mache to create veins and a windpipe and then painted the whole thing, using small tester pots of paint from the local DIY store. Everyone loved it! Can’t wait to do next year’s.