I need help with creating a map in Gimp

[theignis23]

I am very new to Gimp and these forums. I recently got a homework. I have to create a map made out of images. I attached an example image below. I have made few images before, so I thought, that this won't be a problem. I tried cropping a state out of the original map and adding a layer below. Then I coppied an image in place, but it always ended up on top layer.
I didn't know a better community to ask, so here I am. Is there a way to create a map like this in Gimp? Please accept my begginerness.

[rich2005]

Various ways you can build up those areas.  

Start off with a decent size base image that includes select-able areas.  If you have one of those, then assemble the images to go into the areas in a folder.  If you can scale or adjust at this stage it is better but not absolutely necessary. Build up the image by Open-as-layers using the bottom layer as a base.

Then one way.
Add the image layer
Make the selection from the base layer
Onto the image layer and add a layer mask from the selection. This gives some room for adjustment (an alternative is invert the selection and delete)
Kill the selection and apply the layer mask.

That is one area, repeat the process for the other areas. Work from the base layer up-over. All very tedious, take it one area at a time and do not rush.

example https://youtu.be/dgt8BjCgQIk about 5 minutes