Identify a male flower on the squash plant and make sure it’s fully open, or the pollen won’t be ripe. (You’ll know pollen isn’t ripe when you rub the anther with your fingertip and no grains come off.)
Pick the male flower; you’ll be using it as your “tool” to fertilize the female flowers.
Peel back (or strip off) the flower petals to reveal the anther. Gently rub the anther onto the entire surface of the stigma (of your female flower) until it’s sufficiently pollinated. Be sure to work quickly, as pollen only remains viable for a few minutes after it’s taken from the anther.
Repeat with as many male flowers as needed to pollinate all the female flowers.
Once pollination is successful—you’ll know in two to three days and it’s almost a sure bet with hand pollination—the ovary begins to swell and mature into a seed-bearing fruit. And within a few weeks, you can harvest that squash!