I have always used window mounts, which I prepare using a Longridge mount cutter. The actual measuring and cutting gets a bit tedious, but the Longridge does a good job and is reasonably quick.
As to fixing the print to the mount, I have tried a number of methods. For a long time, I attached the photo with masking tape and then used flattened cereal boxes to protect the back of the print.
I then tried using proper backing board, which I secured either with 3M mounting adhesive or a board which was sticky backed. With either method, it was a one shot affair to position the backing board. The sticky backed board was especially tricky both to position correctly and remove air bubbles. There were a few disasters which necessitated starting again with a new print. When using the mounting adhesive, I created temporary hinges with masking tape along one edge to help swing the backing board into position.
Currently, I attach the print only to the top edge of the window using masking tape, then to stiffen the mount I use discarded mountboard such as offcuts and the centres from the windows mounts (it saves waste!) attached using gummed paper tape. By attaching only one edge of the print, it is free to move within the mount to take account of temperature changes. It is also possible to remove the print subsequently if necessary, something which definitely cannot be done when the backing board is attached with any form of glue. So far, so good.