there are ready organic brown rice cereal for baby on the market. Brands like healthy times (found in ntuc), bellamy, organic can be found cold storage as well.
To make your own, you have to wash and dry the rice and then find somewhere to grind it cos our normal blender might not be able to do it.
i have never done it so all the best to you!
Organic stores sells ground brown rice powder. Look for those that need to be cooked over the stove so you'll know it's not instant type (usually for a few minutes to get a nice smooth gluey texture).
Eu Yang Sang also sells ground brown rice powder (needs to be cooked too) suitable for babies, and its added with 四神粉 which is said to simulate and improve appetite.