You can carve it "green" aka fresh and wet, as it will be softer and thus easier to work. Some woods really go from cheese to bone as they dry ( eg Alder = Alnus sp.)
At the same time, you run the risk of your project drying and cracking in progress.
The best you could do is keep the work in a sealed plastic bag to slow down the rate of drying which slows the intensity of the mechanical stresses created in drying.
For seasoning the wood, strip off the bark and seal the cut ends (glue, paint, etc). The idea is to try to even out the rate of water loss
from the sides to that of the cut open ends. Outdoors, under cover and not cooked in a shed, it's usual to imagine that air-drying is about 1" per year.
Thus a 2" diameter stick might have an air-dried moisture content of 12 - 14% in 2 years, 3 is safer. Even so, you should anticipate some end cracking.
Much thicker pieces benefit of course from being split lengthwise to the core of the log.
Get it all set up to be put away and weight it. Write that on the wall. Weigh it periodically.
When it gets down to a constant weight, consider it seasoned for carving.
Never stop looking for new wood.
