Slice lemons thinly (1/4-1/8") and remove any seeds.
Heat water and 2 cups of sugar in a large saucepan or skillet over medium heat until sugar is dissolved and mixture begins to simmer.
Add lemon slices and simmer on low or medium low heat for 1 hour, flipping every 15 minutes.
Remove lemon slices from syrup and lay on parchment paper. Let them sit out for 1 day (24 hours).
Coat with remaining 1/4 cup of sugar.
OPTIONAL: melt some chocolate in a microwave safe dish and dip the sugar coated lemon slices in the chocolate.
Store in a covered container in the refrigerator, with slices between the parchment paper or waxed paper to avoid sticking. If they are coated with chocolate, they will not keep as long. You should eat them within a day or two.
When simmering the lemon slices, use the lowest heat where the liquid still simmers. I typically use medium-low heat, but every stove and elevation is different.
If your syrup becomes too thick while simmering, add additional water to thin it out if necessary.
The thicker the lemon slices are, the longer they may need to cook. Lemon slices are done when the center is translucent and the peel is soft.
The lemon slices will be sticky before coating them sugar.