About this 3D model

Very hard puzzle to solve! All Pieces fit into the frame. But how? Only 9 pieces and still confusing.? !!! SPOILER-ALERT !!! I will share the solution in the comments. Happy Printing ?? I hope you like the parts and i t would be great if you follow me and check out my other projects!? More Puzzles in my Collection Commercial license you can get here: https://www.patreon.com/BamBamDesign/membership