How do I set an executable's working directory via the command line, prior to executing it?

To explicitly set the working directory, a PowerShell solution would be to use the Start-Process cmdlet with the -WorkingDirectory parameter.

Start-Process -FilePath notepad.exe -WorkingDirectory c:\temp

Using the alias start, positional parameter, and partial parameter name this could be written as:

start notepad.exe -wo c:\temp

CMD also has a START command. For this, use the /D parameter to specify the working directory:

START /D c:\temp notepad.exe

The below will work, make appropriate substitutions and save it with a .cmd extension.

@echo off 
C:
chdir C:\desired\directory
C:\full\path\of\command.exe

Put this batch file in a directory in your %PATH% and you should be able to invoke it from any cmd.exe instance.