Making your own lemongrass-infused oil is really simple. All you have to do is take a few lemongrass stalks, remove the outer layer, and crush them coarsely with a mortar and pestle. Infuse this in a jar of base oil (rice bran or olive oil) of your choice, and leave it in a warm, sunny place for 48 hours. Now, strain the oil.
You can repeat the process a few times to get a strong fragrance. Alternatively, you can slow-boil the stalks in the oil to instantly get the essential oil.