Make the jello molds by cutting the citrus in half and then scooping out the center with a grapefruit spoon. This process was much easier for the oranges than for the limes. For either fruit, however, be prepared to get squirted often with citrus juice during this process.
Chop up the fruit for the jello (which can be omitted, if you prefer).
Divide evenly amongst the molds. The first time I made these, I placed the molds in a baking dish. However, the second time I placed them in a small muffin tin and it worked much better to keep the molds from tilting and then having the juice spill out.
Place all the other ingredients in a medium sauce pan and bring to a boil. Reduce heat to medium and let cook for 5-7 minutes. Make sure that all the agar agar flakes have dissolved before removing from heat.
Just when you thought we couldn't improve upon this recipe, we added a shot of vodka to the cranberry juice. There's no stopping us.
Pour the juice into your prepared jello molds. I transfered the juice to a measuring cup with a spout and then poured the liquids to avoid any spillage.
Leave in the fridge for at least 3 hours or overnight.
Once the jello has...well, jello-ified cut the fruit down the center lengthwise (again, this was easier with the oranges than the limes but altogether not that difficult). If you'd like, you can leave them uncut and they'll be fruit bowls instead of fruit slices.