I have found over the years that some hogs just don’t like going into boxes to eat, however hard you try to encourage them.
The best way I found of feeding those hogs which prefer to eat ‘al fresco’ is to use a sheet of perspex type material (has the advantage that you can see through it) balanced either by bricks or earth filled flower pots at the corners and weighed down. The hogs seem to find that as good as ‘outside’, partly I suspect because there are more exit routes if any danger should arise. If you have problems with cats, the height can be adapted so the hogs just fit, but the cats need to creep so low that most (although not all) don’t seem to think it’s worth the bother.
As an alternative you could use the top of a bird table, so that the roof protected the food from the rain – although cats could more easily access that. Or, some people have used those small plastic footstools as shelter from the rain. But you might get away with a feeding box which has two exits/entrances.
I wonder whether your ‘proper hedgehog feeding station’ would do as a hog house instead?
Good luck, I hope you manage to find something that suits the hog.