Cut watermelon rind completely off (no white). I usually cut the melon in half lengthwise, turn it over flat side down, then cut half slices 1/4 to 3/8 inch thick, and finally cut the rind off.
Cut fruit into strips: 1/4 inch thick, 1 inch wide, 3-4 inches long.
Place slices on dehydrator screen, not on rollup films, because you want the air flow to get to both sides of the slices so the melon does not become soggy.
Dehydrate between 24 hours and 48 hours at 115-135 degrees Fahrenheit, depending on your desired consistency.
Lay pieces on wax paper and roll it up like a cigar.
To store long term, roll up those rolls into 3 or 4 inch diameter circles and place in a wide-mouth mason jar.
When jar is completely full, place a desicant bag on top to absorb any excess moisture, with an oxygen absorber in the jar. Seal jar with lid.
You can eat it dehydrated, like taffy or, you can rehydrate it by placing strips into cold water for about 3 hours.
When it is rehydrated, the fruit will be flimsy (not crisp) but it will have a fresh melon taste.