Quarantine itself actually wasn’t as horrible as I had imagined. Is it boring at times? Yes, but you know what your hobbies are and what you like to do in your free time. So bring them!
It’s a great time to read, Netflix is accessible and you can start learning Korean. Working out is always an option (water bottles make great makeshift dumbbells), you can journal, do puzzles, listen to music, etc.
My room was relatively small. The pictures show it’s basically just a bed and bathroom with a tub that also had a clothes line, so if you can bring a small bottle of clothing detergent you can do some laundry. I used bar soap to make the water soapy, but wished the whole time I thought ahead and brought real liquid laundry soap.
I would suggest bringing a thermometer. You do need to take your temperature twice a day for the app they have you fill out. I wasn’t able to get my hands on one until day three of my quarantine, so I was always putting in my temperature from when they took it at the airport. They ended up bringing a few of us a kit later on with a thermometer, hand sanitizer, a spray sterilizer/deodorizer for the garbage you will accumulate and have to sort, more masks, and information (all in Korean).