Edit: Yes, using a DEM for a bigger area worked. However, now I'm getting crazy slope values, everything is around 90 degrees. It's a hillside vineyard, I don't think it's vertical.
I am trying to create a slope from a clipped DEM. The DEM is for a small plot of land, as you can see below. Each square is 30x30m.
The slope map is not registering values, just going from NaN to NaN.