Choose mature corn kernels
Clean and wash the kernels thoroughly
Soak the kernels in water for 24 to 48 hours
Drain the soaked kernels
Grind the kernels with fresh water into a fine slurry
Strain the slurry through a fine cloth or sieve
Collect the liquid containing the starch
Let the liquid sit undisturbed so the starch settles
Pour off the clear water from the top
Wash the settled starch with clean water
Let the starch settle again
Repeat washing and settling until the starch is clean
Spread the starch on trays or a clean surface
Dry the starch completely
Break up any clumps
Grind or sift the dried starch into a fine powder
Store the corn starch in an airtight container