Merge Cube and Google Slides


I need a little help to figure this out. I am a newbie to this and am happy I got this far! I am using Google Slides to create presentations. I have sized it to 5x5. I have downloaded each slide as a jpg. I have uploaded to Cospaces/Merge Cube. The question is how to make sure the slide is attached to the cube. I know how to size and right click to attach and lock but generally when I rotate the cube, I see a slight gap. When I attach too close, it disappears into the cube.
Is there an easy way?? --I am hoping to use this with 5th graders. Thanks!