I would like to make a custom brick for a decorative purpose. It will be painted so the material is not important, meaning it doesn't have to be a clay brick, could be concrete like cinder blocks. I can make my mold very easily but I am unsure about the mix to put in. These instructions are for clay bricks and require a long time of curing them in the sun, and I have neither time nor sun at my disposal.
If I were to pour my brick with some cement-based material (like concrete), what ingredients and ratios should I mix and how is that the mix (if any) different from a regular concrete mix? Also, is there a way to make a clay brick faster than the instructions submitted, since I need only one I could cook it in my kitchen oven for example? While concrete is acceptable, clay would be slightly preferred if not much harder to work with.