A Flower Press! Recommended to use PLA + (Plus/Pro/Professinal, depending on the brand), ABS, or PETG. I printed mine out of PETG and PLA+. I believe regular PLA doesn't have the flexibility and will likely break, but I haven't tested it personally.
I've known of flower presses ever since I was a little kid, but never actually used one to press flowers. I created this one because I had a need to press things and well, a flower press seemed ideal! I have not actually used it to press flowers specifically though. Hopefully this serves all the needs people would need for a print like this. It's been serving me well.
A note on the bolts! The clearence is tight, and so the first time screwing one in, it might feel really tight. I work the bolts in and out a few times to loosen everything up. Since we're clamping, I didn't want things to get too loose.
Enjoy!