My original mugs were formed in this way. These days I use slabs and bisque molds.
I start by forming the clay into an egg shape.
Then I make a hole with my thumb and pinch out the walls until it looks like cup or a bowl.
Later, I carve away more clay to thin the walls. I smooth the ridges with my fingers.
Using a measuring tool and a cutting tool at the same time, I even out the rim and shape it. After that. I turn the vessel over and trim the bottom.
Last, I add handles and my signature on the bottom.