creating the forum isn't the difficult part, incel forums have very low standards compared to older forums
generally the sites have only a few boards, and a simple design
keeping it going is more difficult. since companies might be reluctant to host it and you might need alternative solutions. but even the kiwifarms survived, so I think it should be possible if you pay attention to which services have proved trustworthy on the anti-censorship front
there are a few incel forums, and ones like .club manage to keep going without too many difficulties. plus incel sites don't typically face much as much cendorship as the kiwifarms, and can even use some common services like cloudflare
even nathan larson's ring of pedocel websites did grnerally managd to stay up, until it was taken fown by internal conflicts with anothef incel
tl;dr creating the site isn't so difficult, finding members + keeping thr site going will be more of a hassle