The lamp is a frustum of an N-sided pyramid. Export pane STL writes one side as a plain trapezoid slab whose long edges are already mitered. Print N identical copies and they close into the lamp with no gaps.
Side miter is the bevel on each side edge, measured from the face perpendicular. A straight hexagon gives 30°, a square lamp 45°. Thickness grows inward from the outer face, so the outer trapezoid is always the exact frustum face.
Horizontal cut keeps the rims level; Square cut leaves the rims perpendicular to the pane. The window is a straight cut-through; turn it off to get a solid slab to carve up yourself.
The lid and base are N-gon slabs that sit inside the panes. Screws go in from the outside: each pane gets a through hole and the slab edge gets a blind pilot hole, both sized from the one screw size (M3 = 3). Print the lid and base as exported, step up; the pane STL carries the screw holes too.
Each plate is one piece with a glass step: the full-width section touches the side panes and takes the screws, and the step on the inside of the lamp (on top of the base, under the lid) is narrower by the glass thickness. Slide the glass sheets in between the panes and the step walls so they stand on the ledge. Set the full-width height and the step height of each plate separately; the readouts give the glass cutting sizes.
The decoration section adds ornaments cut from the pane itself: a crest above the top rim, a skirt below the bottom rim and a patterned window. Each zone has ten designs; use the arrows (or Left / Right when the control is focused) to cycle through them, 0 is none. The crest and skirt height set how far they rise and drop. They print as part of the pane, so the pane STL and the whole-lamp STL include them.
The pane decorator (View, Decorate, or Open decorator in the Decoration section) places free-form shapes on the pane the way you place shapes on a slide: drag to move, handles to resize and rotate, Cut to remove material (a round hole in the frame, say), Mirror twin to repeat a shape across the centre line. The 3D view beside it shows the whole lamp as you edit. Shapes apply on top of the crest, skirt and window presets and print as part of the pane, so the pane STL and the whole-lamp STL include them.
The bulb bracket hub is a disc in the base's centre hole, held by spokes, for a lamp-holder bracket; its hole takes the lamp nipple (10 mm standard).
In the export, +Y is toward the top of the lamp and the origin is the middle of the footprint. Outer face down puts the decorated face on the print bed.