rectangular photo frame 3d model

Create a clean 3D printable rectangular photo frame insert for an alphabet photo frame. Overall size: 70 mm height, 50 mm width, 6 mm total thickness. Make a smooth front photo window with rounded corners and one simple raised border, no multiple inner steps or extra layers. Back side must have a simple flat recessed pocket for the photo and a thin sliding back cover. The back cover should slide in from one side through a side opening. Use smooth 45-degree chamfered side guide channels/rails so it can print flat without supports. Avoid horizontal overhangs. Add a small rounded retaining bump, friction stop, or tiny end notch at the end of the slide path to stop the back cover becoming loose or falling out. Keep it simple and printable, not a complex latch. Smooth edges, clean geometry, minimum 1.5–2 mm wall thickness, STL-ready, no text, no decoration, no colour.