we did this experiemnt... we did that to c the stomata, guard cells and how it is affected by weather, temperature etc...
first we get like a layer of nail polisher on the leaf's epidermus and allow it to dry... then, we just peel off the nail polish and the epidermus along wif stomata, guard cells are peeled off with it... then u gotta do like, standard slide thing and prolly a drop of water to prevent it from overheating from the microscope...