eBay is generating my labels on 8.5"x11" standard paper/letter size
instead of 4"x6". I can't find where to set the default to 4"x6"
anywhere in Seller Hub. No, it does not show up when you're on the
shipping info page before you purchase the label.
I called eBay support tonight. It's the 'Switch to Advanced Shipping'
button at the top right of the shipping page as you purchase your label.
I originally declined it because it just mentions additional carrier
services. Problem solved!