First, thank you for replying. The slices in your picture are so clean, which makes me wonder why I couldn't. It seems that cutting is a common problem in making biscotti, so your experience would be very valuable to share.
what is it like after you bake it at 350 for 20 minutes ? Is it crispy outside and wet inside, or is it wet both inside and out? I find it particularly hard to cut if the crust has become hard but the inside is still wet.
The reason I used a lower temperature is because I added in some olive oil which cannot stand heat that well. I compensated it by baking longer.