Because there's no single definitive location, the best way to find it is to:
1. Consult your owner's manual: This is the best starting point. The manual should have a fuse box diagram showing the location of all components.
2. Locate the fuse box: This is usually under the dashboard, often on the driver's side.
3. Inspect the fuse box and surrounding area: Look for a small, easily accessible component that matches the description of a flasher relay. It might be labeled.
4. If you can't find it easily, search online: Use a search engine with the terms "1992 Ford E150 turn signal flasher location" along with any specific trim information (e.g., "1992 Ford E150 Econoline turn signal flasher location"). Images and forums might help.
If you're uncomfortable working with electrical components, it's best to take your van to a mechanic.