Printing and assembly

Use your basic slicer settings with 100% infill. If you are using PrusaSlicer I recommend using Concentric top fill pattern for separated poppy, but for simple poppy use default monotonic pattern. Poppies look best when printed from red and black filament using a color change function. You can also print whole poppies from red filament and then color the center with some marker or black color.

Assembly is also simple, you just have to glue a brooch pin (like this one) to the groove on the back side. I also uploaded versions without grooves if some wanted to use different brooch pins.

Wearing

There is an article about wearing poppies on Wikihow that sums it up pretty well. Or you can decide to follow simple instructions from Royal British Legion:

We often hear people debating the 'correct' way to wear a poppy, but the truth is, unless you're currently serving, there is no 'correct' way. 

It’s a matter of personal choice whether someone chooses to wear a poppy and how they choose to wear it. We simply ask that if you do wear a poppy, you wear it with pride.

If you print one of these poppies, please consider sending donation to Royal British Legion.