In a salad bowl or directly in your large pitcher, place the lemon slices and the sugar. Cover with boiling water. Mix then leave to rest covered for 30 minutes.
Meanwhile, squeeze the juice of the remaining 2 lemons and the 2 limes.
Once infused, remove the lemon slices (pour the contents into the pitcher if you haven't already). Add the juice of the squeezed lemons to the pitcher then 1,5 liters of cold still water.
Optionally, you can add fresh mint leaves for an extra touch of freshness.
Cover the pitcher and place in the refrigerator for at least 30 minutes.
When serving the lemonade, place ice cubes in each glass and lemon slices for a colorful touch!
Notes
You can keep your homemade lemonade for up to 3 days in the refrigerator, ideally in a closed pitcher with a lid.