Quite frankly, overlay map projects confuse me and I need step by step instructions.  But I was able to figure out how to apply the idea to a project which would interest us.  When we studied the Great Flood, we learned about mountain building and the massive erosion that created river beds, piles of fossils crushed into each other and covered with mud, huge canyons, etc.  We decided to do overlays on the major geographical features of today that probably resulted from the Great Flood.

We started with a base map of the world. This can be printed on paper or cardstock, although I didn't realize that and printed it on a transparency.  When I did that, I realized I needed a paper backing of some sort so it would stand out. 

Then we got a fresh transparancy, hole punched that and added that to the 3 ring binder, on top of the base map.  The dc colored with a yellow sharpie, the deserts of the world. Then on a piece of yellow paper (lower left corner) they numbered and listed the major deserts.  Then they were numbered in black on the transparency (so they could all fit.)   The dc glued the yellow paper with the key to the desert information onto the transparency in a place where it would not be in the way of any information.

The next layer is for the mountains.  They used a brown piece of paper to list the major mountains of the world.  Then they used a brown sharpie to number these locations on the map. They could have even drawn some upside down v's for mountains.  I think they didnt' do that because there were already some on the base map that I used.

The next layer is for the rivers.  They used a blue piece of paper, with a list of the major rivers.  Then with a blue sharpie, they drew in the rivers and numbered them.

The final layer was for the Oceans.  For these they did not use any color coded paper.  You see a blue paper but that is the one for rivers showing from underneath.  For this layer they took a dark blue sharpie and wrote in the names of the oceans.

For our resource we used A Beka's 5th grade history text, Old World History and Geography.