It appears you could finish two 1/2 platters with a little smoothing of the edges.
So cracking... it is a problem that every beginner faces. Here is a list of things that promote cracks (things not to do)
-- over working the shape
-- bending or carelessly handling the leather hard piece
-- joining pieces with lots of slurry
Here are some good practices:
++ making a solid, smooth lip
++ leaving pieces to dry (no touching!) after the leather hard stage has passed.
The most valuable constraint in my first ceramics assignment was a height requirement. This challenged me to make pieces that were bigger and opened many doors. The current challenge (9 tiles) does this well in a different way. There is a fixed requirement within a very vast world of possibility. Also tiles make excellent wall art and help fill the often blank walls at a show!
An early university assignment that I wouldn't mind doing again: an organically inspired piece that is 12" (30 cm) or taller.
Does a piece get rejected for being 11"? Nah... just working at this scale is enough.
It can be done on the wheel with alterations (not decorations) or hand built.
Seed pods, vegetables and gourds are excellent starting points.