Photos show that the Israeli flags they are burning are not close to what the real Israeli flag looks like - the blue stripes reach the border of the flag and the Star of David, perhaps symbolically and perhaps antisemitically, is broken up.
They couldn't have imported these flags from Israel, which means that somewhere in Gaza, someone is manufacturing hundreds of Israeli flags to burn.
Which brings to mind this German satirical video I once added subtitles to:
Meanwhile, women in Gaza are joining the festivities by painting their shoes as Israeli flags.
I don't know, it looks sort of fashionable to me.