Roger is absolutely correct. In fact, I’d like to add some observations about practicing on mounds at schools and your local ball field.
99% of every pitcher’s mound that I have observed in the amateur game, is junk. Absolute junk. The bad habits and self taught compensation while working of these things - or worse, the acceptance of this junk as a medium to learn on, is a joke.
Flats can offer you a different perspective on how to develop a reasonable style and how to manage your movements. Flats don’t have the holes, butchered surface, and worst of all, the influences of those that went before you that are somewhat raked over - if that. Schools, playgrounds and municipal ballfields have neither the resources, the desire to learn, nor the fundamental interests, to do better. Besides, a good pitcher’s mound requires constant maintenance, of which, goes well beyond the mowing, raking, pickup trash, and in some areas - constant vandalism.
A very good friend of mine offered to construct and build a professional pitcher’s mound at a local high school. After spending almost $700 for materials and supporting grounds work, within the first season of use, it was right back to a pile of dirt with holes in it. The municipal civil servants got their nose bent out of shape because someone was taking working away- thus did nothing to maintain all this work and expense. Couple with the “I could care less” high school coaches and their students who left the mound uncovered after every use - the cover by the way cost about $ 140, and eventually got stolen.
So, learn with the flats.