Get a nice-sized walking stick and a big bundle of dry straw or hay. I think there's a specific plant called broom sedge or Scotch broom that's been traditionally used, if you can find some. It smells kind of spicy and nice. Stick the stick into the middle of the bundle, covering the first 6-8 inches. Bind it tightly with twine around the top of the bundle, and at least one more time about 4 inches lower than the first tie. You can add more if you like to shape the broom however you want, the further down you tie it, the tighter and more round it will be
A four foot dowel one inch in diameter
ball of twine
straw or other long strands of pliable herbs
Take the straw, or another herb you have chosen for the bristles, and allow them to soak overnight in warm, lightly salted water. The water softens the straws to make them pliable, and the salt soaks out former energies.
When you are ready to make your besom, remove the straws from the water and allow them to dry a bit, but not so much that they lose the suppleness you will need to turn them into your besom.
Find a work area where you can lay out the length of your dowel, and begin lining the straws alongside the dowel. Starting about three inches from the bottom, lay the straws, moving backward, along the length of the dowel. Begin binding these to the dowel with the twine. You will need to tie them very securely. You can add as many layers of straw as you wish, depending on how full you would like your besom to be.
When the straw is secured, bend the top straws down over the twine ties. When they are all gently pulled over, tie off the straws again a few inches below the original tie. Leave the besom overnight to allow the straw to dry
The dowel part of the besom can be stained, painted, or decorated with pagan symbols, your craft name, or any other embellishments you choose. Dedicate your finished besom in your circle as you would any other ritual tool.