Fill a small saucepan or double boiler with 1–2 inches of water.
If not using a double boiler, put a heat-safe measuring cup in the pan so the water reaches roughly halfway up the sides. (If you don't have a measuring cup, you can put a heat-proof glass bowl on top of the saucepan.)
Pour the carrier oil into the measuring cup or the top of your double boiler. If infusing your carrier oil, place the herbs into the oil, and simmer for 30–60 minutes. Strain out the herbs and return the oil to the pan.
Add the beeswax, and heat on low until the beeswax has just melted. You don't want the oils to get hot, just warm enough to melt the beeswax. To speed things along, stir occasionally with a spoon or wooden skewer.
Once the beeswax melts, remove it from the heat and pour the oils into a clean bowl. Let the oil and beeswax mixture cool to room temperature. The mixture will begin to turn cloudy and thicken as it cools, so you'll want to stir as needed to prevent it from hardening and keep the beeswax mixed in. If you're in a rush, place the bowl in the refrigerator and check on it every 5 minutes or so until it feels cool to the touch and the mixture has thickened.
Measure out your lavender hydrosol, and with the immersion blender running and submerged in the oil, slowly drizzle it into the oil mixture. Pause the blender every now and then to scrape down the sides and reincorporate the oils. Continue blending until the oil and hydrosol are fully combined and your lotion is the consistency of icing.
At this stage, you can add any of your add-ins, like aloe vera or essential oils. Then blend again, so they incorporate evenly.
Before transferring the lotion to the bottle, spritz your container with rubbing alcohol and turn it upside down to let the alcohol run out. This will keep bacteria at bay and ensure your lotion lasts longer.
Use a funnel to transfer your lotion into a clean, dry storage container. The lotion can be a bit runny, so a pump bottle works best.