[String7th]

The room is not acoustically bad as far as being odd shapped.

Here's a starter for ideas in this pic I made.
Center the desk longways and bring a foot or 2 away from the wall. The bass traps or accoustic pannels can be as simple as rigid fiberglass or mineral board covered in fabric and mounted on the wall. If you know your way around home depot, buy some spacers for the wall panels so it hangs a couple inches off the wall for lower frequency trapping.

Also what I didn;t draw in the picture is you will want those same cloth covered boards over the listening position.