When you stain a stock that has incise carving, and/or relief( raised) carving, you expose a lot of end grain along the sides of the carving. The end grain will take more stain, and will look darker than the surface area of the stock.
That is where to first begin.
Next, if the contrast is Not ENOUGH to your liking, then add additional stain to just the carved portions, to darken them. Do this in stages, and let the stain dry. Then you can wipe the stock with a wet cloth to see what the stain contrast will be after you apply your stock finish to the entire wood.
Take your time, and darken the carvings slowly. Its very difficult to remove the stain after its applied, if you get it too dark.
There are some guns made where Black Dye is used on the carved and "checkered" areas, to make those "Pop". I don't particularly care for this kind of contrasting, as I think it hides good and BAD carving work, and detracts from the flow of the grain of the stock, which I like to see through the carvings. But, to each his own....... :surrender: :thumbsup: