If you have your own trees, have someone saw them for you.
Step 1: Dovetail Jig
The easiest and fastest way to notch the logs is with a jig
My site has plans to build your own if you want : http://logdovetailjig.com . By building your own, you can have a custom set of jigs that will work for your particular log dimensions and end up with the gap between the logs that you want.
Our example cabin for this instructable is 11'-8" x 16' using logs that are 7" thick x 9" high. The gap will be 2.5 inches. Yours could be other sizes. The plans are custom designed for whatever dimensions are specified.
After you decide on the cabin dimensions, add 4 inches to each and use those numbers to cut the logs to length.
So the logs for this example would be cut 12' and 16'-4".
The jigs shown are for half dovetail notches and take about 2-3 hours to make.
Step 2: Attach the first jig
Lay the log on a side and mark a line down the center using a chalkline. The jig also has a centerline marked on it with holes cut out that make it easy to align the jig with the log.
The jig attaches to the INSIDE face of the log. (The face of the log that will be on the inside of the cabin. This is facing upward in the photo)
Leave about 2 inches between the end of the log and the jig end piece. Attach it to the log with 3 sheetrock screws.
You will measure from the perpendicular edge of the jig as shown in the photo.