get a little piece of a mirror
put the bike in gear and hold the brake if the window is on the left side of the bike
sit on the seat, bike vertical, reach down with mirror - easy
this is a good time to point out, because the oil filter fills with oil when the engine is run, and depended on which bike you have it may slowly drain out after the bike has sat (over night, over a week...) its best to check your oil after you have rode a few miles, let it sit for minute to let the oil drain down from the heads, then check it
if you check it then, check it in the morning again - if its the same then just check it in the morning from then on
the potential problem is, if the filter slowly drains out and you check it, it will look hi, or full when its not.
BTW< if you want to stand your bike up to work on it, get a couple 4x4s or a 4 x 6 and a 2x4 block of wood andand make a solid stack of blocks that fits under the frame on the right side of the bike (just behind the engine, lean the bike up on it solid, then slide some wood under the kickstand to hold it level