A craft fair is a shelf that lasts one weekend. For small ducks, the table has to explain the theme in a second, and you have to be allowed to sell what is on it.
Only bring what you can sell
If the file is personal use, it stays home. If you have an active commercial license, physical ducks are fine at a market. The Duck Heroes license includes craft fairs and conventions when that license is actually in force. It does not include handing someone a USB of STL files.
Keep a copy of the license with you. You will rarely need it. When you do, a calm one-page explanation beats an argument.
Set the table for small objects
Put ducks at chest or eye height. A flat cloth at knee level hides faces. Group a series together so the shared eyes read as one family. Leave space. Twenty ducks touching each other look like a bin, not a collection.
A small mirror or a raised board helps. A handwritten size card helps more. People ask “how big” before they ask the theme.
Say what it is
“3D-printed collectible. Display piece.” That sentence prevents the bath-toy assumption. If a character is a fan interpretation, do not letter the sign as if a studio licensed you. Themes and legal selling are the same rules in a tent as they are online.
Price and packing
Mark prices. Mental math in a crowd leads to discounts you did not plan. Use the cost sheet from pricing. Bring simple bags for people who carry the duck home, and boxes only if you are shipping later. See packing.
Take payment the way the fair allows, and count stock before you leave. A missing duck is either a sale you forgot or a lesson about the edge of the table.
You do not need a banner of download counts. You need light, a true sign, and ducks you are allowed to sell.