The latest tip I read for clean slices of biscotti was to allow the loaf to cool thoroughly before cutting (with a very thin, sharp serrated knife). The first loaf cooled 30 min. before slicing per recipe instructions and was crumbling badly enuf that I diped the knife in water before each cut, hoping the moisture would Help soften the crust. Maybe? (I had even used an extra egg for a softer dough.)
OK, next loaf you are going to cool completely even tho it may be a total waste. Hmmm, just in case I'll cover you with a damp paper towel, oops, awfully damp. Forgot it for 2 hrs. Best slicing job I've done in 25+ years. Here's the photo with only 1 gouge! Think it was a craisin that pulled away.