There tons of ways to do this, but you have to remember simple is elegant, even if it just feels quick and dirty.
+ System: Start of layout
-> Function: Set return value to 0
+ MouseKeyboard: On Left mouse button Clicked
-> Function: Set return value to Function.Return+1
+ System: Function.Return Equal to 1
-> Sprite: Flash for 5 seconds with 0.05 seconds interval
+ System: Function.Return Equal to 2
-> System: Go to layout 1 with transition "None" lasting 0 MS