I usually leave about 1/4 inch of the stem on the root above the last growth ring. I have dried roots before in a spare room of the house, with all windows open to keep the breeze circulating. Keep them out of direct sunlight. I put mine on a frame with window screen, so they are lifted off the ground and can get air underneath them. After about 5-10 days, I usually go flip them over, being very careful not to break off any root hairs. (I don't know why it matters, when I give the roots to the dealer, he grabs them in handfuls and all the root hairs break off anyways).