It's important to try to get your slices the same thickness or else some will dehydrate faster than others. Just do the best you can.
You don't have to leave them in rounds. You can half or even quarter the round slices if you want.
Sliced and ready for the dehydrator tray.
You can dehydrate limes. lemons and grapefruit or citrus fruit the same way.
Then I have my heavy duty dehydrator, the Excalibur 3900B 9 Tray Deluxe Dehydrator which has an internal fan and 9 trays. It does an amazing job and no need to rotate trays as the fan distributes the heat evenly.
We believe in being self-sufficient if there is ever a long-lasting emergency or crisis situation. So I dehydrate many fruits and vegetables for use if that ever happens. They will last a very long time and all you need do is check them every so often for mold. Don't open the jar, be sure you use glass so you can spot check without disturbing the food items.