Zest the lemons into a bowl with the sugar. Zest means no white part! Only yellow part! Use a vegetable peeler for quick work. Muddle (or “mash”) the zest around with the sugar until the sugar looks damp and the peels are all covered in sugar. The point is to get the essential oil out of the lemons (and into your liver, eventually). This is called oleo saccharum, or sweet oil; set it aside for 30 minutes.
Juice the lemons and measure about 5 ounces of juice. Strain that into the oleo saccharum and stir it wildly and with abandon. Just kidding. I mean, stir it thoroughly and have some self-control. Once that is dissolved, strain out the lemon peels.
Add all your boozes. Like David said, if you have no pear liqueur, use apple; if you have no rum, use whiskey; if you have no friends, more punch for you. Mix it all around again. Add the water. Taste it and see if you want to add more lemon or sugar. Plop in the ice block and stir it around to chill it. Cheers!