Does anyone have any suggestions for a good tool to use for creating a map from individual tiles? I’m looking for something that will make it very easy to lay down the tiles and put them together into a single image file for importing into my Foundry Game.
If you have your own tiles - my crude way is to use Google slides to build and then take and crop a screen shot 
Some folks use Tiled to make their video game levels. I can’t truly recommend it as I haven’t used it myself, but it might be worth a look.
Campaign Cartographer is basically that.
Note that you WILL want to read the tutorial, the software is based off a CAD mentality and framework. There are periodic Humble Bundles where you can get it for cheap.