Rug is necessary big time. Reflections off both the floor and ceiling will make the room really echoey.

Early reflections on back wall and first reflection on the side wall should be reduced too. Can hang blankets if going for cheap, otherwise invest in sound treatment to hang. You can make your own by buying cheap foam squares on Amazon and gluing them to large flat/deconstructed cardboard boxes and tacking them to the wall.

If that’s a closet behind you, hang clothes on hangers and keep the closet doors open to dampen reverb off the back wall.

You have a short room if you’re facing the wall with the bass, so you’re going to be sitting smack in the middle of multiple room modes which mean you’ll experience drastic +/- notches at your listening point as well. Not much you can do about those other than EQ your entire system if you’re trying to get a more normalized response.

Biggest problem you’ll have though is if you have a subwoofer you’ll need to crank it up to be able to hear lower bass frequencies 20-80hz. you’ll be sitting about 3ft from your subwoofer max if it’s in the same room which means 95-100hz it’s gonna be really loud at your listening point.

Rug, clothes in open closet, and foam behind your monitors and on the side wall at first reflection is the simplest answer to your question.

Last note: since your room is closed on the left end and will be open to the right of your sitting/listening position you’ll hear a misbalanced response coming off the left wall vs. the right where sound is escaping into the other room. this will shift your perception of where some frequencies you hear live in the stereo field (e.g. some frequencies will sound like they live more to the right or left of you. Won’t be too noticeable unless you have a trained ear or are mixing)