Cut down the tree in such a way that you don't shatter it when it hits the ground.
Let it sit 6 months or so to start curing.
Slab the wood 5"-6" thick.
Air dry (preferable) or kiln dry the wood.
Cut into 16" wide x 48" long pieces.
Seal the wood, let it sit a year or so to stabilize.
Cut into 2.5"-3" thick pieces.
Cut into a 3" X 8" X 48" stock blank.
Now here's the critical part:
Find a stock carver who can rough carve the stock blank and rough inlet it for the action you intend to use.
Inlet the stock, shape and finish the outside of the stock.
Total time from tree to rifle= 3+ years.