How do you make your hair straight without a flat iorn?

Try blow-drying it. Use a brush and while blowdrying brush your hair straight down.

Another tool that might help is shampoos and conditioners that have straightning advances.

You might want to use conditioners that weigh your hair down, which will get rid of some of the unwanted body.

You can also choose to go down the chemical road, and get your hair chemically straightned.