Put up a cell shade on the window. Close the shade. Staple black poly around the inner window frame.
Install a closed cell shade on another window, that's visible from similar spots on the outside of the house. Open that shade half the time. No one will notice. The more complicated you make it, the more suspicious it will be. On the front of my house I have a bathroom facing the street. It's got identical cell shade to other bedroom that's also facing the street. Bathroom shade is never open. Ever. No one notices that. Ever.
When you're building boxes with random light timers and defused LEDs behind false net curtains, your next step is "Well, I need to now project a silhouette of a person into the window every once in a while or else people will notice."
People will notice foil cardboard and paint on the glass of windows. That's it. Oh yeah, they'll notice grow lights shining out if it's not covered, that too. But that's about it.