So, this morning I had to drive across a snowy field to collect the trailer. I engaged the low box and diff lock, and set off slowly, aiming to neither spin the wheels nor stall. However, everything went really juddery, with the wheels appearing to stick and slip repeatedly. On occasion, I lost all traction and was spinning two wheels at once, so had to go back a bit and try again (this of course got even worse once the trailer was coupled, and TBH I think I was pretty lucky not to get stuck completely at one point, even though that's really not a huge depth of snow).
On looking at the tracks I left (pictured), it seems that the tyres were gripping the snow ok, but were then shearing that snow off in chunks and throwing it behind. At the points where I had been unable to move, it seems that the snow had not sheared off at all, but had just become a compacted slippery patch, which the wheels then skidded on.
So, help me learn folks. How could I have done this better?