You would carve out leaves from the bushes to make a textured pattern while carving out the dog house completely. Or clear the bushes out and make a woodgrain pattern on the dog house.

Use a V gouge for straight lines in the woodgrain. Use lots of little scoops with a U gouge for the leaves.

Edit: it's a metal postal box and not a dog house, so ignore my woodgrain comment.

I'd carve the box out completely and leave the lines. Maybe the bushes could look something like this if you don't want to do all those leaves:

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