Using the pre-folded square filters, hold three of the four layers and pull the fourth layer forward to open the filter into a cone shape. Place the thicker side over the spout of the brewer, and set the filter in the Chemex. Pre-wet it with hot water off the boil (about 205*, just before it begins to bubble) to heat the glass and remove the paper taste from your brew. Toss this water without removing the filter and breaking the seal it has with the glass.
Weigh and grind your beans, about 25g of coffee/ 3 tablespoons.You will want the grind looking a bit coarser than drip coffee (granulated sugar) but not as coarse as french press or cold brew. Add the grounds to the Chemex and shake it to level the coffee bed. Put your set up on a scale and tare it out.
Start your timer and pour into the middle of the bed with a slow pencil-thin stream. Wet all of the grounds in a circular motion, then stop pouring and let the coffee bloom (de-gas). You may help the bloom by gently stirring the grounds to wet any dry pockets near the base of the cone.
Begin pouring again after the timer hits 30 seconds, in short 10 second increments, avoiding the walls of the filter. Keep the water level about the same throughout the brew, without letting it drain completely until the very end. When you reach 370g total weight on the scale, stop pouring and give the Chemex two slight spins to catch the grounds hanging on the filter walls.
At the 4 minute mark, you can remove the filter and pour yourself a hot cup of coffee.