I should think there are plenty of better explanations than mine , but here is how I do it.
Best stuff to use is birch twigs cut in winter when the sap is down and the leaves are gone. I have used hazel twigs and a few others depending on what I had around . I either use Ash or Hazel for the handle , again depending on what you have about .
First collect a bundle of twigs cut to the size you want the broom head to be . Then I use galvanized fencing wire to tie it up into a bundle . You collect the twigs into a nice tight bundle and then wrap the wire 2 or 3 times around the thick ends a few inches from the very end . Twist the ends of wire together very tight , so as to really tighten the twigs all together . Then move along the twigs 2 or 3 inches and do the same again , remember to make the bundle as tight as possible , I mean really really tight , then do it a third time. You can use split fresh cut willow or ash to do this , but I always break them trying . Tuck the twisted ends into the head , after trimming if needed.
Next you get whatever you are using for the handle, and peel off the bark if you haven't already done so . You can leave it on if you want to , but I find it can make your hands sore if you use it with the bark on . Anyway , make the handle the right length for you , and sharpen one end , like a pencil .
That end is then placed as near the center of the thick top end of the broom head as possible . You then just knock it in . Easiest way I found was to push it in by hand first , then turn it upside down , so the end of the handle is nearest the floor , and holding the broom head where the wire is , lift and tap the handle on the floor , thus knocking the pointy end into the broom head .
You can then either knock a 2" or so nail through the handle and the broom head between the rows of wire , or drill a small hole through the handle and knock a wooden 2-3" pin through ( like a thinnish pencil ). Knocking the handle in the head should make an already very tight head even tighter , and the pin or nail will stop the head from falling off. Job done ....
Thats how I make them , and they work fine .
Hope it helps ...
cheers
Russ