These flags print flat to minimize number of color changes thus decreasing both printing time and filament waste if they were printed vertically instead with the wave already to them. In order to form them to be wavy, use this form which you print in PETG to bend. Flag Wave Form

If you do not want to make them wave and just display as a plate. I have holder model to hold them standing up as well. Flat Plate Holder for flag designs

Print the flags face down like in the supplied print profile to get a better front surface finish. Print them in PLA so they can be heated and pressed into shape post process. The flags print as solid plates as I tried (accidently) with just infill on one print and it did not look or bend as nice.

Note that one can clone the flag and print two on same build plate for A1, P1P, P1S, and X1C if want two of them.

To bend with printed form, heat flag with heat gun back and forth a little while until flag is softer then quickly apply top form and make sure the lip on it catches the bottom of flag and press up and check that top of flag is flush with top of form. I clamp mine and let it sit for several minutes to cool down and keep the wave form but one can also just hold for a minute or two. All the flags in my profile are designed at the same size to work with the same form.

Under my profile I have both a square flag pole Square Flag Pole and a round one Round Flag Pole, so you can choose whatever your preference is or print one of each to accompany your flag.