Preheat your oven to it's lowest setting, or to 200 degrees F. The lowest setting on my gas oven is 200 degrees, so that is what I used for this recipe.
Using a mandoline*, slice your pears crosswise (horizontally) in 1/8th inch slices (or just shy or 1/8th inch) until all of the pears are sliced. You can slice the pears by hand if you don't have a mandoline, just make sure the slices are uniform so they dry consistently.
Discard the very end pieces and remove the seeds from the inner slices.
Arrange the pear slices in a single layer on wire cooling racks or wire drying racks. Sprinkle the pear slices with cinnamon or other spices if you are using them.
Move your racks to the the oven and bake for about 60-80 minutes, or until the pears are completely dried. Keep close watch on your pear crisps since the bake time will depend on your oven and slice thickness. If your lowest heat setting is less than 200 degrees, then it will take longer. If your pear slices are very thin*, it will take less time.
Turn off the oven heat and let the pear crisps sit in the oven for another 30-60 minutes to continue drying without heat.
Store in a sealed bag or container. Enjoy!
Notes: Slicing your pears to less than 1/8 inch will make them dry faster, but they may end up too fragile and crumbly if they are too thin