If you’re not going to soundproof everything, hit the surfaces closest to the microphone (leopard print optional), then the room’s opposing surfaces. Then, if you can, everything.
That’s my joke about once having an office with surgically perfect white walls and no rug. I could clap loudly once and go to lunch. The clap would still be bouncing back and forth between the walls, floor and ceiling when I got back.
This is where the closet recording studio comes in. Leave the winter coats in there and announce around them.
If you like the idea of a tiny studio, behold the Kitchen Table Studio.
https://forum.audacityteam.org/t/too-compressed-rejection/52825/22
That is the affordable Home Store version of a commercial product.
https://voiceoveressentials.com/product/porta-booth-plus
Most home stuff isn’t heavy or dense enough to make a studio. Most light, fluffy blankets let sound go straight through. Packing material doesn’t work—too light. Each of the moving blankets in that posting weighs as much as two gallons of milk.
Carpeting works. If you have a carpet store in your neighborhood, you can pay a visit after hours and dumpster dive.
Koz