I marked a proposed plinth shape on the new piece of stone and cut (with a saw) a couple of pieces off the sides to straighten up the edges.
I drew on the stone my idea for the shape to go on top of the plinth but I'm not definite about this yet.
I'm going to see over Xmas if I change my mind and decide to put something else on top of the plinth.
I gave one of the sides of an offcut a bit of a polish to see what colour it would be when it is finished.