In these days of readily available printing, we're old school traditionalists who still make most of our stuff by hand (with the aid of relevant tools!) - a case in point being whenever we need a new size or shape of base.
The collage above illustrates the process. Left to right from top:
Cut square length of chemiwood.
Chamfer square into octagon, cross cut one end.
Tenon cut the same end to leave a machined peg to fit into the lathe chuck.
Machine corners from octagonal stock material.
Reduce size of material until desired diameter is achieved.
Cut relevant profile onto the end of the material - DS/bullnose in this case.
Machine desired recess into face.
Mark cut-off point with pencil while spining the lathe.
Cut off base with parting tool.
Sand underside of finished piece until flat; set aside for moulding.