As a rule, kit log homes and notched log homes require that you cut keyways and leave settling space when installing windows and doors.  That is true for Saddle Notched log homes, Scandinavian Chinkless style log homes, and Appalachian or Dovetail style log homes, because they all experience settling.  

A keyway is a slot cut into the window and door bucks.  The slots allow lag screws to slid down, as the log wall experiences settling.  If there was no keyway, then as the log wall settled the the lag screw would damage the windows and doors in your log home.  The diagram below shows how the lag screw can slide down in a keyway: 

Settling space is an area above the window or door frame (see Fig A below).  It allows the log above the window frame to get lower (due to settling) without damaging the frame.  Normally a slip-joint is created with lumber, in which the window is installed.  Fig B shows a Butt and Pass log home, where the windows have zero settling space. 

There are some real downsides to doing keyways and settling space.  If the keyways and slipjoints are not done properly it could result in severe damage to your windows and doors.  If your walls settle just a little bit more than expected... severe damage.  Also, cutting keyways and making the slip joints is a bit complicated and time consuming (it slows the whole project up). 

It would be a lot faster if you could simply cut an opening in the log wall that is just the right size for the window, and then slide the window into place.

Luckily there is one traditional method of log home construction that does not require keyways and slip joints: the Butt and Pass style of log home construction.  A properly built Butt and Pass style log home will not experience settling, so no need for keyways and settling space.

Below is a picture of the door on a Butt and Pass log home built by one of our students  Notice that there is no settling space above the frame (the frame is made from 4x12s).  The 4x12 at the top is touching the log above.

Here is a close up:

The bucks (the 4x12 uprights) have no keyways cut into them. 

Not having to accomodate for settling saved the builder a lot of time.  Saving time was important, because this student had to build his home during a summer vacation.  Since he was building a Butt and Pass log home he got his shell up in less than 30 days, working alone, and he moved into his home a short time later.