I disagree. You control the attitude of the bucket with the dirt you're moving. If the left side of the bucket is low... you dump some dirt in your left side wheel tracks to raise that side of the bucket. Once you get the get the bucket on the plane you want, it digs out at that angle. Then you can turn around and sit on the "level" area you just dug out to dig out the "launch pad" you created to set the bucket angle.
I said hard not impossible.