@d7bow I started off using a cheap light mallet that I like to round the edges with.
I lightly tapped the edges and the willow virtually folded under the mallet. As it was so soft I've only used the light mallet up to now, and haven't really given it a good wack yet!
I plan to get rid of the indentation shown using the light mallet, then move onto my LV mallet to finish up the process. I'm thinking of this time using the cheap mallet as a pre-knock before I properly knock it in.
This is definitely the softest bit of willow I've ever knocked in, so I'm going to take my time and make sure I get this one fully prepared. The process will take longer than usual, but it taps up well as it is, so I'm hoping my time and effort will be rewarded with a pinger!