Wet your filter to get rid of any papery flavor and then pour out the water.
We want to keep within the 1:16 ratio so we need 800g of water. This can be divided between ice cubes at the bottom of the Chemex and hot water for extraction. With 400g hot & 400g ice the iced coffee will come out cold with a bit of ice still intact.
Grind 50g of whole beans to a medium-coarse consistency (about an 11 on the Hario Mini Mill) and place them in your Chemex.
Using boiled water like you would with a normal Chemex, wet the grounds from the center out to the edge without reaching your filter, pausing to let the grounds bloom. When the dome of grounds has deflated, continue pouring in a spiral, using about 1/3 of your water at a time.
Pull up a couple of glasses, grab a friend, and have a toast to the sun with your freshly-brewed iced coffee.