Most lavaliere microphones are non-directional. They depend on closeness to the performer to do their tricks. This works on large news sets or other acoustically dead or controlled environments. If you record in a bathroom, it’s going to sound exactly like recording in a bathroom.
I made really good use of furniture moving blankets for two projects: The kitchen table studio…
https://forum.audacityteam.org/t/too-compressed-rejection/52825/22
…and a portable studio.
https://www.kozco.com/pictures/boothFinished/laptop-mic.jpg
“Heavy” is good. Each blanket is 7-8 pounds (3.5kg) each.
Libraries full of books work well. I made good use of a storage closet full of paper accounting records.
Lots of bare walls, ceiling and floor are not good. This room would be a nightmare to record in.
This room would also have a different problem. If two people talked to each other across that room, they would be perfectly loud but would not be able to understand each other.
There are more exotic solutions, too. Flynwill, one of the helpers on the forum once designed a sound studio without parallel walls. It had normal acoustic ceiling tiles and a little carpeting, but was amazingly dead for sound recording. Only if you were paying attention did you know that the north wall was slightly bigger than the south, east and west walls didn’t line up and the ceiling wasn’t level.
I sent a lot of sound jobs through that room.
Koz