Automator use current directory location
Have your workflow figure out its own path (more robust)

This works as long as your Automator workflow lives in the same directory as MyApp.app; you can create copies of either the workflow or the app at your discretion and reuse those copies wherever you want; nothing needs to be unique.

Steps

These are the steps to automate launching MyApp.app:


Open the workflow in Automator.
Add a Run AppleScript action. Remove all the boilerplate code inside and replace it with the following lines:

set AppleScript's text item delimiters to ":"
set appPath to (text items 1 through -3 of (path to me as text) &amp; {"MyApp.app"} as text)
tell application "Finder" to open file appPath

Save the Automator workflow in the same folder as MyApp.app.
Run the Automator workflow; it should launch MyApp.app.


Explanation

set AppleScript's text item delimiters to ":"


This means “Watch out, I’m going to split a string soon; and I want you to use the : character as the split boundaries.”

path to me as text


This instructs the workflow to figure out the path to itself; path components are delimited by a colon (:), which is a remnant of Classic Mac OS.

text items 1 through -3 of […] &amp; {"MyApp.app"}


This cuts off the last part of the path, and appends MyApp.app to the path.

[…] as text


This pieces the path back together (again with : as a delimiter).

tell application "Finder" to open file appPath


Lastly, this final line causes MyApp.app to launch.