Ask Lemmygrad

Get a somewhat thick white PVC pipe (its walls should be like 2-3 mm thick). If you are unsure about the thickness just make sure it doesn't bend easily. Cut it to about one and a half length your height. If the flag has a seam to insert it into poles like that just place it in. Otherwise, if the flag has holes in it for rope, drill the pipe. Or if you dont have a drill, take a nail, heat it up until its point is red and use it to drill through the pipe. It'll penetrate it like butter when hot. Then use zip ties to get the flag in place and carry some additional zip ties and a cutter to swap flags.

If you are making the flag from scratch, and you have access to a sewing machine, then fold one end of the flag about 5-6 cm and sew it to make a sleeve. Then sew the top of the sleeve to close it off on one end. That way the pole can fit in the sleeve and hold the flag.

PVC pipes work fine but if it's windy they'll sway really bad, or wood dowels if you're allowed. You should double the flag on itself at the end so that it creates a tube (then glue or staple to itself) and you can then insert the pole into it. I don't know if I'm being very clear, this is the flag seen from the top:

From what I understand flags have this shape in them already if you buy them, if you're making them then account for it that it's gonna make your flag a tiny bit smaller.

It's very makeshift, the flag can slide along the pole or even detach like this (you should add something at the top of the tube so that it doesn't slide down the pole), but it works fine for protests and such.

Need eome symbolism.