the 'sandwich flip'
The best way to flip any relatively flat leather hard piece:
I use cut pieces of 'foam topper' (which is a mattress pad) under my sculptures while I work on them. The foam allows a form to be supported but not misshapen.
To turn a piece over, I 'sandwich' another piece of foam plus a batt over the top, place one hand on the top board, one hand under to support the bottom board and then flip everything together in one motion. Less stress on the piece means less chance of cracking in the firing:)