No Supports Needed. A sharp eye will notice the vent holes are staggered vertically to avoid all landing on the same layer. =) 40mm top hole. Make sure your material can take the temp!

Get the whole look:

Overhang Bracket https://www.printables.com/model/430914-edge-overhang-brackets

Slip-On Shade https://www.printables.com/model/437200-slip-on-hanging-lamp-shade-vase-mode

Worried about HEAT? I let it run for HOURS with a 30-watt LED Grow bulb and it never got soft or smelled.