In this example, I always see two squares when trying to look behind it, never 4 like the instructions require.
How can I let my eyes focus behind the screen? I can focus my eyes in front of it by looking at my finger, and get 4 squares that way, but that doesn't work for focusing behind it, for me.
No planet appears when making it 3 squares while looking at finger in front of it either for me. And if I remove my finger, my eyes immediately change their focus :/
No tips - except at a guess 10 or 20% can't and won't ever see them.
I spent ages trying to make these things work in the 80s or 90s whenever the posters were the craze. Never got close, and there were quite a few others they simply didn't work on.
http://www.magiceye.com/faq_example.htm has some helpful instructions (you're looking for a planet with rings)
Would be useful if it had some markers for achieving the correct amount of focus.