I think you can still walk around if you put holes to check where the plot is going to be, but that uneven corner is suspect. If you can dig a hole in that spot or put flowers and paths, there'd be no question. But it seems like you can't so I'm not sure if you can put a villager house on there. There's no harm in trying, I guess? Since you can just TT back to the previous day to edit paths and stuff.
I've never had any luck with tting backwards with plots, either with ds clock or the game clock, but I plan in plot resetting and I have everything covered with tiles so hopefully...