The following is step-by-step information to curl hair with a flat iron.
Products necessary for the process:
Blow dryer: using a ceramic or ionic tool is the best option to reduce the damage and dry time.
Clips: Apply jaw clips as they can seize large amounts of hair securely.
Thermal Protectant and Styling product
Comb: A professional comb has no seams that tend to break hair.
Flat iron: choose a straightening rod with rounded plates having smooth strands of hair and ceramic plates to seal.
Process
In the beginning, get ready the hair for curling. For this, wet the hair. Since too much moisture prevents hair from holding style, dry it prior to applying the flat iron. To minimize the heat damage, let hair dry naturally or blow dry thoroughly and make use of thermal protectants. Spray a heat protection on the dry hair right before the application of heat.
Comb hair gently to remove the tangles. With jaw clips, clip top hair and leave the remaining bottom in a fringe around the head. Take a vertical or horizontal section of hair and spray lightly with a thermal protectant. Then fasten the flat iron near to the scalp and draw iron half a full turn. If using a horizontal section of hair turn iron away from head. Move iron in either direction if using a vertical section. Slowly pull the iron through the entire length of hair until ends of the hair slip through the iron's plates. The slower the iron is pulled, the tighter the curl will be. It will create loose curls and twists if you pull the iron through quickly. Make sure that the iron is pulled right through ends or hair parts will be curly with an inch of straight hair at the bottom. Wait for hair to cool prior to styling further or re-curling hair. Trying to re-curl the warm hair won't work. Likewise, trying to add accessories or style products to warm hair will cause the curl to droop and loosen.
Before and after each pass of the flat iron, comb your hair with your fingers or a wide-toothed comb. Do again all steps until all hair has been curled.