Slice pears super thin and remove seeds. In a saucepan on medium heat, heat sugar, water, and lemon juice until sugar is dissolved. Place pear slices in the sugar/water mixture and cook for about 3 minutes. Remove pears from the mixture and drain. Meanwhile preheat oven to 225F. Spray two cookie sheets with cooking spray and cover them with parchment paper. Lay pear slices in one layer on a cookie sheet, spaced evenly. Place pears in oven for 1 hour, flip slices over and cook for another 1 hour or until mostly crisp. Remove from oven and allow to crisp up. You can also turn off the oven and allow them to cool and crisp up in the oven.