Gather your supplies: one small Mason jar and the oil of your choice. Olive oil and grape seed oil are two options.
Harvest enough mullein flowers to fill your small Mason jar. You don't need to prepare a large jar of mullein flower oil because you need only a few drops at a time to treat an ear infection.
Set the flowers aside for a few hours to allow some of their water content to evaporate.
Transfer the mullein flowers to the Mason jar.
Fill the jar with oil until there's no space left. Screw the lid on the jar.
Place the jar in a location that gets sun all day. The next day, pour more oil into it if the level has dropped. Cap it tightly. Leave the jar in its sunny spot for a minimum of 30 days and a maximum of 60 days.
Strain the oil and store it in a clean bottle with a dropper. Having a funnel for this operation prevents an oily mess. Keep the bottle in a cool, dark location.
Collect some mullein flower oil with the dropper. Apply a few drops to the infected ear. Plug the ear with a small cotton ball to prevent the oil from leaking out.