How do you make an essential oil diffuser?

It is not something that is easily made, though you don't have to use a diffuser for essential oils. You can light a candle, and when the wax on the top is liquefied, poor the essential oils into it. You may want to blow the candle out whilst you do this, as the drop are extremely flammable, and you need to avoid the flame.

Pure therapeutic essential oils should not be heated. Heat will destroy the beneficial properties. If you cannot afford a $35.00 diffuser, then simply apply the oil to a kleenex and lay out or put it inside your pillowcase. On the road, I use a napkin and three to five drops of Peppermint and stuff it into my air vent. It keeps me alert for many miles as the oil fills the cabin. It is also effective enough to just put the oil on a standard saucer and leave it to the open air in your room.