Starting on page #20 of the attached link, you can see a stock go from block-of-wood to gunstock.
http://garagegunsmithing.com/index.php?option=com_jfusion&Itemid=56
I've done a fair number of stocks and the absolutely most difficult to do are those with a finished outside and 0% inside. The problem is that you have to make the inside match the outside. Starting with a block-of-wood allows you to fit the inside with nice square surfaces to hold/line up to/measure from and then you just whittle the outside to the desired shape. Here's a mini-project I did making a new grip for a Dan Wesson Revolver.... the principles of inletting remain the same.
http://garagegunsmithing.com/index.php?option=com_jfusion&Itemid=56
The principles are to make sure of each cut before you do it, measure often, don't rush the job.
I use the mill as much as I can to keep things square but if you are doing it with hand tools, use a square to confirm you are keeping it square.
What are you thinking of sinking into the stock? What tools do you have at your disposal? If I knew the action and the workshop, I could offer a bit of insight on where to start.
Here's one I raised from a puppy (glued layers to make laminate, etc...)