I have been making leaf patters from slabs for several years.
With reduction firing, I would lose half of the platters through cracking.
I tried drying the platters on sheetrock, running the slab through the slab
roller in EVERY direction, making sure all slabs were greater than 1/4" but less than 1/2" thick, and even changed glazes.
I was about to abandon making them when I read an article about making square plates. Each plate had the sides compressed.
I now compress the sides before manipulating the edges. I use a round bisque "wheel" that has an incised pattern.....you can make these yourself. I also put decorative "stress lines" on the bottom of the platter
(these are much like the stress lines put in concrete floors).
I still dry the platters on sheetrock and cover them with plastic .
I want them to dry from the bottom down (prevents warping).