Those are great James!
I am absolutly no professional ,but instead of proping the knife up and trying to get the right angle just try rotating the camera.
Also try backing off the knife then zooming in to get rid of shadows.
The reason I say this is I struggle taking shots and these are the things the pros are telling me.All and all they are great pics just thought this might help.and if you've got a lot of walnut like that I sure could use some.