There are two methods you can use to propagate your aloe vanbalenii successfully and those are by either taking cuttings or by using seeds.
When using seeds be sure to sow in summer using well-drained soil. Your best option is to use 1/2 of river sand mixed with 6mm sieved compost. After mixing your medium you should level it and then sprinkle your seeds evenly across your tray. This will help prevent overcrowding. For protection, it is highly recommended that you use a fungicide to prevent damping off. Cover your seeds lightly with your soil mixture. You must be sure that your seeds will receive sufficient light, ventilation, and water. Your seeds will probably start germinating after 3 weeks or a month. Once your seedlings have reached 20-25 mm in height you can prick them out into pots, and then using the same medium as before transplant them into an area where it will get full sun. Use liquid fertilizer to feed your aloe and remember that they need to be planted in bags placed under 20% shade net when they reach a height of 50mm.
You can take cuttings from the parent plant, however, do not plant them instantly. You must let the cuttings heal for a minimum of one day. When you are planting your aloe dip the cuttings into a rooting hormone that is suitable for semi-hardwood cuttings and then insert it into a sandy medium. After placing your tray in the glasshouse it should only be watered twice a week to prevent rotting. It should root after about a month. Once the rooting has started, you should plant the rooted cuttings into a well-drained soil mixture, for example, 2 parts compost 2 parts sandy soil, and one part loamy soil. Be sure to place your pot where it will receive adequate sun.