There's no magic bullet for free speech thanks to the Paradox of Tolerance. Allowing all speech, completely unrestricted, is a recipe for creating a completely unworkable environment.
In the "Paradox of Tolerance" Popper argues that despite the apparent paradox, defending free speech and having a tolerant society is the only way to go. People use the paradox of tolerance argument often, but leave out the part where popper resolves the paradox.
Popper essentially takes the same position as Thomas Jefferson. Popper says: "I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be unwise." Emphasis on the unwise -- for some unknown reason, there's this idea floating around that Popper thought it was wise to suppress intolerant philosophies. That's Marcuse's position, not Popper's (and Marcuse also is candid that his own position may be incompatible with democracy).
What Popper does agree is that societies should retain the right to act if civil discourse fails, which is again basically Jefferson's position.
More briefly: When the intolerant reach for a gun, the tolerant don't have to tolerate that. Not when the intolerant speak - when they proceed past speech into violence. Then the tolerant don't have to tolerate it (and, in fact, kind of have to not tolerate it.)
>Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.—In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise.
>But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols.
>We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.
The one thing one may claim is that it is not immediately clear is what he means by intolerance or intolerant groups, yet he leaves little ambiguity in the second section above.
I'm going to assume that you've read the meme cartoon that goes around instead of actually reading Popper's actual words because that is not what Popper suggested at all.
It's only a couple of pages long, it's even free to read on archive.org.