Slice the leftover turkey into quarter-inch-thick slices. Anything less than a half inch will work fine.
In a large skillet over medium-high heat, sear the slices of turkey and add some stuffing or turkey dressing to the pan. These should already be cooked; this process is just to warm the meat that will be in the middle of your crunchwrap. Once it is warmed to your liking, remove everything from the pan to a plate and wipe out the pan to be used later. Remove the pan from the heat and add your 12-inch burrito tortilla to the cooling pan for 1 minute per side to warm it up and make it more pliable.
On a cutting board or clean, flat surface, lay down a 12-inch burrito tortilla and add the slices of your cooked and re-warmed turkey in the middle. You can use your corn tostada for reference, but you basically only want to add ingredients in a circle in the middle six inches of the 12-inch tortilla.
Add some of the stuffing/dressing or mashed potatoes to the top of the turkey.
At this point, everyone will have different types of leftovers, but the goal is to layer them in a stack that makes sense to you. If possible, sandwich the crispy tostada between layers. Drizzle on gravy and cranberry sauce if you have them, and sprinkle some crispy fried onions to add more crunch and flavor.
Here's a quick animated image of how I built my crunchwraps. Basically, the gist is just that you need to layer everything and make sure you get the crispy tostada in there to give the wrap the "crunch."

Wrap your crunchwrap: Fold the sides of the flour tortilla up over the top, meeting in the middle. The image below shows a crunchwrap with cheddar cheese being folded, but it's the same concept.

Once folded, you can flip the crunchwrap over to retain the folds and shape.
In your large skillet over medium-high heat, add a teaspoon of oil.
Sear the bottom, folded side of the crunchwrap in the oil to seal in the goodness.
After 2 minutes, flip and sear the other side for 2 minutes. If either side isn't quite browned enough for your liking, you can flip and cook for an additional 1 to 2 minutes on each side.
After at least 4 minutes of cooking, and when both sides of the crunchwrap have a nice, browned exterior, serve and enjoy.