I wonder if you stretched out a chamois or maybe a piece of soft buckskin and then poured the slip on it. It would have to be a dedicated piece because I doubt the clay would come off cleanly. You just need something to suck up the water.
All of these methods have merit. All worth trying.
Since today was a very low humidity day, I tried what might be the same as solar heat collection tech.
When the sun shines, light rays hit dark objects and heat them.
Objects lacking pigment reflect the light.
I had good overhead declination and a bit of a breeze. A better wind would have worked better for convection (air movement). Think convection oven that you can actually cook in.
What surprised me today is that the oven did not to do much drying?
The dry moving air was the remedy.
It's late so I'll post the photos and process soon.
Zuma
PS I need to post this one