To use the service download it, unzip it, launch it, give permission , install it, and then go to the Keyboard System Preferences to add the Ctr-Cmd-K shortcut.
 This is how tiny it is
tell application "Slack" to activate Since this Service is not signed you will also need to override the default restriction on unsigned applications using the Security & Privacy System Preference. Go to its General tab and press Open Anyway button next to the text
tell application "System Events"
keystroke "k" using command down
"SlackCommandK.workflow" was blocked from opening because it is not from an identified developer."