If really looking for a cheap user friendly level find a clear glass mug with horizontal rings on it, fill with beverage of choice to one of the ring marks, hold steady so liquid is level on the ring mark and sight along the top of the liquid level. Works well if you can stand a little downhill.
I have used this method once when there were no levels on site. It worked well but due to having to keep the liquid/foam level even on a rim the beverage supply ran out and had to be refurbished.
In the picture the flat leveled area is under the trailer and a portion of the road is level but slopes downhill.