Heads up, instance blocking doesn’t do what you think it does. I just want to make this clear because a lot of people suggest it without having read the announcement on the join-lemmy page or the dev comments on github and get a less than accurate idea of what it does. From Join-Lemmy:

Users can now block instances. Similar to community blocks, it means that any posts from communities which are hosted on that instance are hidden. However the block doesn’t affect users from the blocked instance, their posts and comments can still be seen normally in other communities.

It isn’t a souluton to the Hexbear spam problem and this is something people should remember and keep in mind when suggesting it as an alternative to defederation.