Slice watermelon in half, remove rind, then slice into strips ¼"- ½" in thickness. The thicker you make the slices, the longer it will take to dehydrate them.
Arrange watermelon strips on dehydrator trays, leaving room for air circulation. Set the temperature to 135F. Depending on the thickness, it can take anywhere from 12-24 hours; Flip halfway through.
When the cooled watermelon jerky snaps when it's bent, it's done. If not, continue to dehydrate unless you prefer it bendable and chewy rather than crispy.
Allow watermelon jerky to cool completely on wire racks before storing it in airtight containers, ziplock bags, or mylar bags. Toss in an oxygen absorber.
Notes
If you don't have silicone tray liners for your dehydrator, you can use parchment paper.
You can start and stop the dehydration process to check the texture of the cooled jerky. It's hard to gauge the texture when the jerky is still warm.
If you prefer a chewier texture, slice the watermelon into thicker slices ½" to ¾" or dehydrate the slices for less time. Keep in mind that if there is a lot of moisture remaining, the jerky won't keep as long.
One advantage to slicing watermelon into thinner slices (¼") is that it will significantly reduce the dehydration time. I don't like to wait, do you?
Keep in mind that smaller pieces will be done sooner than the larger ones.
To keep the watermelon from sticking to the trays, consider using mesh screens (tray liners) or lining the trays with parchment paper.
If you need to, you can turn off the dehydrator overnight and restart it in the morning.
Store watermelon jerky in a cool, dark pantry in an airtight container for up to 3 months.
Place dehydrated watermelon in the freezer for longer storage.