You will need
A four-foot ash limb for the broomstick
Willow (the long strands to which the leaves are attached) for binding the broom end to the shaft
Brush from a birch for the bristles
Water and salt for soaking
Soak the herb you'll be using for the bristles overnight in warm, lightly salted water (to make them pliable). Allow them to dry a bit before using. They should be damp and pliable when binding the broom. Should they get too dry, soak them some more.
Line the straws alongside the limb, about 3 inches from the bottom. THE BOTTOM OF THE BRISTLES SHOULD POINT TOWARD THE TOP OF THE BROOM. Begin binding these around the broomstick with the pre-soaked willow binding. Tie them very securely. Add as many layers of bristle as you want, depending on how full you want the broom end to be.
Bend the top of the bristles over the willow twine. When they are gently pulled over, tie the bristles again just below the fold. Leave the broom overnight to dry.
Decorate the broomstick, if you wish, with your magickal name, magickal symbols. Consecrate the finished broom as you would any ritual object.
Other materials are often used for the besom, including
Masculine trees suitable for the broomstick: Hazel, Oak, Rowan
Feminine herbs suitable for bristles: Myrrh, Mugwort, Thyme, Willow branches
Cotton or hemp twine can be substituted for willow strapping.
Consecrate the finished broom as you would any ritual object.