Did this for the first time last week. It took a lot of time and was extremely messy. The kids were good, though, and cleaned up well. I will do it again next year because it was the only thing in social studies they got excited about this year.
Salt dough is easy.
Two parts flour to one part salt. Dump out and knead until smooth. Add food coloring a few drops at a time and knead to mix. I teach fifth grade. I made a transparency of the US and projected onto the whiteboard in a size to make Rhode Island large enough to work with.