Gay asked how I finished off the square dishes so I thought I'd put this sequence up.
This first image shows the bottom of the pot after it has reached the leather hard state.
I basically hand trim it with a loop tool. Just cutting away the clay on each side in turn. I don't do this with the wheel turning, I just use the tool to remove the clay. A Sure Form rasp would be another tool you could use.
The finished pot. I smooth the edges with the side of my thumb.
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This first image shows the bottom of the pot after it has reached the leather hard state.