I glue them to Gatorfoam using a fabric glue called Miracle Muck.
Lay the print out on a piece of Gatorfoam that is a few mm smaller than the print on 3 sides, but a few hundred mm longer on one side. The print should be hanging slightly past the Gator on three sides. When the print is aligned, tape it down all the way across on the side that is longer than the canvas. Roll the print up on a tube. Using a VERY THIN 200mm foam roller roll out 12ml of Muck for each square foot (you have to saturate the roller first, takes about 80ml). Applying slight tension and pushing slightly downward, roll the print out on the glue. Rub down print with a cotton gloved hand. Press down any fabric bumps with a pointed burnisher. Have a pin ready in case of air bubbles, but if you rolled out the print correctly you will not have any air bubbles. The print will warp towards you for a few hours, then flatten out perfectly. You must use only Gatorfoam, regular foamcore will warp horribly and stay that way forever. The reason the print should be slightly larger than the Gator on three sides is so you don't pick up glue on your hand while you are pressing down the print near the edges. This works REALLY GOOD! I can mount several large prints in an hour, using $6.00 worth of tools.
Next day I put the mounted printed in a nice classic frame that I cut with my beat up Morso Chopper, or maybe on one of the better saws at the shop. I don't even like to remember how hard it was to frame regular prints.
Or, if you enjoy worrying, you can stretch your prints on canvas stretcher bars and wonder how long it will take for them to sag.
Of course, the canvas must be coated before gluing. The biggest nut to crack regarding canvas is coating.
You can also drymount canvas in sections using tissues like Fusion4000. IMHO too much work and too hot.