Hey Aaron,
If you select an item in the Finder and run this script:
Putting relative-aliases on the Clipboard
It will assemble this part of the code for you and places it on the Clipboard:
alias ((path to downloads folder as text) & "YourFolderName")
You can run that script from the Script Editor.app to see how it works.
Essentially it takes a known location (path to...) and converts the resulting alias to a string.
That string is an HFS path.
From that anchor-point the script appends the rest of the path (from the anchor) to the file or folder.
The “alias” in front of that turns the full HFS path into an AppleScript alias.
Once you've selected a few items in the Finder and run the script to see how the paths differ, place it into an Execute an AppleScript action in a Finder-specific Keyboard Maestro macro – give it a keyboard shortcut ⌃⌥⌘P (or whatever is mnemonic for you) – and go-to-town.
--> is representative of a result in AppleScript.
set hfsPathStr to ((path to downloads folder as text) & "Test Folder:")
--> "Mercury:Users:myUserName:Downloads:Test Folder:"
set destFldrAlias to alias hfsPathStr
--> alias "Mercury:Users:myUserName:Downloads:Test Folder:"
Most Mac-users are terribly confused by path strings when first exposed to them. Don't let it bother you if you're one of them.
You have to use them a bit, before they start to feel comfortable. It probably took a year before using them became second nature to me – and that was back in the days of only HFS paths. When OSX came around so did POSIX Paths and a whole new set of issues, and again it took me a while to get comfortable with them.
-Chris