Harvest your leaves on a dry, sunny day. Pull off any parts that look sick or diseased and brush off dirt with a dry cloth if needed. Arrange leaves in a single layer on a clean, dry surface (best lined with a towel even though I forgot to take a photo after putting it down) and allow them to air dry for 2-3 days. When the leaves are dry and crisp, start step 3.
Chop the leaves or place them in a food processor and pulse a few times until they are coarsely chopped.
Place ground leaves in a clean, dry pint mason jar and cover with oil. The oil should completely cover the leaves.
Cover the jar with a lid. Place a kitchen towel in the bottom of your crockpot and place your jars inside. Add enough water to cover about half the jar and set to low heat. I recommend the lowest setting possible, which is the "keep warm" setting on the slow cooker I use. Leave the slow cooker uncovered and allow the oil to infuse for 2-6 hours, adding water if needed to keep the slow cooker basin from drying out. Give it a shake (to help the plantain infuse faster) if you think about it whenever you walk by. (In the photo there are two jars because I was making a double batch.)
Remove the jar from the crockpot and strain the oil through cheesecloth or a fine mesh sieve. Let the oil sit for several hours. If there is any water in the oil (from the plantain leaves) it will collect in the bottom of the jar. If there is any water in the oil, use a turkey baster (if you have one) to siphon the infused oil off the top, leaving the water behind. If you don’t have a turkey baster, carefully pour the oil off the top.
Give the cheesecloth a good squeeze to extract as much of the plantain-infused oil as possible.
Now that your plantain oil is ready, gently heat the beeswax in a double boiler. When it is melted, add the plantain oil while taking care not to pour in any water that may have collected at the bottom of the jar. Stir until thoroughly mixed. If you're adding essential oils, wait until the mixture has cooled a bit and then stir them in.
Pour your salve into a clean, dry container and allow to cool. Now you're ready for the next bug attack, bee sting, or brush with poison ivy!