Before you store them, clean them with a bit of detergent and some water. That's all they need, no special dressings. These next steps are the ideal, but we suspect most people don't store tyres perfectly so don't worry if you can't.

Bag them up in an airtight bag and make sure there's no moisture in there. And make sure they're kept out of direct sunlight. This reduces evaporation of oils from the rubber compounds. Then you can either stand them upright like you're doing, hang them up or stack them on their sides. The best option is standing, as it puts less stress on them. When it comes to your method, I'd just make sure they're out of direct light and moisture and away from any heat sources. Tyres age regardless, so just do what you can to extend their life.