Back a few years ago when I was making (and trying to sell) custom "Round Saver" shell holding blocks, I slabbed the green woods and had them dried in a local firewood (drying) kiln. Besides Cherry and Maple burl wood, I used Brown and White Ash, Yellow and White Birch, White Pine, Eastern Cedar, and Hornbeam. If any of you have ever slabbed a burl, you already know it's the worst! Besides voids, I've found: dirt, fungi, leaves, twigs, mold, moss, water, and in one - a dead mouse!
Anyway, the slabs went in with a room full of green firewood, and in 7-10 days were ready. Surprisingly, very few cracks developed in the woods as they dried. As soon I got it home I cut them into blocks, then brought them into the house so they stayed dry until I got around to finishing them. Unfortunately, all that effort was a waste of time, since only a few ever sold.

But hey - it was fun making them, and I have enough blocks to last me three lifetimes!
Chris Mitchell