I haven't done one in a while, but if I was to do one now I would go about it like this:
1) File front of toeplate, where it will go completely into the wood, with about a two degree taper along the edges so the bottom is slightly smaller than the top. Leave the sides that will show straight. Remember that the stock will widen as you cut away wood and make sure that it is wide enough to cover the stock completely when inlet - i.e., larger than the uncut toe.
2) Place toeplate on stock and scribe around the part where the sides will be inlet. If you are inletting a simple rectangular plate you can ignore this.
3)Draw or scribe lines on either side of of your stock at the proper depth.
4)Carefully file away the excess wood down to your lines, leaving just a little bit to go and angling the file up a bit so you don't take chips of the opposite side. Do this on both sides.
5) Cut away the lump in the middle of the toe left by the file and slightly hollow out the center, so only the edges will touch the plate. There are multiple ways of doing that - I personally would use a a good sharp chisel to pare away most of the lump, followed by a shallow gouge or a rough scraper to hollow it slightly. With a narrow toe like I suspect you have, you may not need to remove much - the point to take away is that only the edges need to touch. I would leave about a 1/16" or a little larger flat on either side.
6)If you are using anything other than a rectangular plate, cut a rough inlet inside your scribed lines for the front part of the toe.
7)Coat your toeplate with transfer color and inlet straight down, using files, chisels, or scrapers to remove wood at the bottom of the mortise, until you reach the proper depth. Ideally, it will be showing black along the edges, but still slightly hollow in the center of the inlet. Of course, if you didn't hollow it out deeply enough the first time you can always scrape out a little more...
8) Screw it down, file the edges to match the stock.
I apologize if some of this is too elementary.