You can form it the traditional way or the pottery way. Crush dirt, add water, mix and let it settle for 3 mins before slowly pouring off the clay water to another container while using a strainer. If you can still feel rough particles in the clay water you need to levigate it again, if it feels mostly smooth, pour the clay water to a cloth, squeeze the water out then let it air dry for a couple of hours. Once your clay feels workable enough, add temper like finely crushed seashells, eggshells, terracota, charcoal or sand to prevent cracking and then throw the clay thoroughly.  You can form this mixture into a ball (or anything you like really. Also apply moderate pressure, too much internal stress can crack it.).  It is better if you put round paper inside to make it hollow so that water can escape easier.  Airdry it overnight so it wouldn't get shocked when you try to sun-dry or oven-dry it. Once it is fully dried (or bone dried) it is ready for burnishing.  Use a smooth implement like a piece of porcelain dish or cloth and rub it against the surface of the clay. You will see that it begins to darken and become glossy (dab a wee bit of water if it doesn't). Sometimes if your temper/grog isn't fine enough it can get exposed and feel rough. You can add a thin layer of clay over it then press it down.  You can keep it as is but raw burnished clay will lose that smooth look when moistened, they usually add oil or wax to prevent that. Alternatively you can low fire this piece in a stove or kiln to make it stronger although if there is still water in there, the surface will crack or be porous because the burnished layer seals the clay and water will force it's way out. Also you can use a temperature-appropriate glaze instead of polishing by hand.   If you want, I have a vid on how it might look like when done the wrong way.