Once the gesso is sanded to a very smooth surface, a number of layers of red clay are laid down where the gold is to go.
This clay is itself sanded finely and polished up with wire wool.
23.5 carat gold leaf is laid using the water gilding method. (Alternatively oil can also be used, producing a different finish.)
The gold is then burnished up to a shine.
The same technique applies to any shapes for gilding.