Here's how we do it.
1. You punch/strike/kick a firm, smooth object with a bit of give to it for a certain period of time. Doing that puts callouses on your stricking surface.
2. You move to a firm, rough object with a bit of give to it for a certain period of time. That thickens the callouses on the stricking surface.
3. You move from a firm, rough object with some give to it to a thin, solid, smooth object with no give to it, like a few pine boards put together or a rebreakable board. That thickens the callouses even further.
4. You move from a thin, smooth object with no give to it to a thicker, rougher object with no give to it. Think a thin patio block. If you want the thickness to increase, you move from thicker smooth object (Thicker pieces of wood) and then move to a rough object with that same thickness.
5. Sooner or later, you're now breaking bricks.
Be sure to do some strength training and isolate the tricep muscles. Those are the muscles you depend upon to break boards with punches and other hand strikes (Knifehands, palm strikes, spear hands, hand thrusts, arc hands, ridgehands, etc).
So far, I can break a floor tile with a straight punch and I can break a patio block with an axe kick and a side thrusting kick.