The boxes are for banners so i use colompac 108 x 108 x either 610 or 705mm.
Yes the text will only be the website address and basic logo.

There are essentially 2 views on how to work Etsy.

1/ As many products as fast as possible and advertise everything with loads of money.
2/ Don't do the above.

A link to a chap who is the second option.

https://www.youtube.com/@etsyconsultant

I have linked to that as there are gazillions of ...