Original is here: https://www.thingiverse.com/thing:1056164

I used Fusion360 to round off all edges possible with a 1mm fillet. That was the only change I made on the Flag_Base.

On the Flag_Halves, I did the same with the fillets, but I basically re-modeled the entire thing since the original model didn't convert so well in Fusion360. After that, I added a square peg on one side, and a square hole on the other side of the circle hole. Then, I mirrored it so that the hole and the peg were reversed. I also increased the size of the hole by .2mm on each side so that the peg fits snugly in the hole. I felt this was a logical thing to do since it makes assembly a literal snap.