The standard 38 mm LED tealight is designed to be snapped into the candle holder from below for use.

There is no need for glue, as the tealight can be easily removed from the top.

Print instructions
Filament: PLA
Print: 0.2mm
Nozzle: 0.4mm
Perimeters: 2 
Infill: 15% 
Support: Not need

Print instructions flame and tree
Filament: PLA
Print: 0.2mm
Nozzle: 0.4mm
Perimeters: VASE MODE 
Brim: (i used for flame)
Support: Not need

Filament: Prusament pla: Lipstick Red, Oh My Gold, Pristine White, Galaxy Green, Mystic Brown