You must have a permit.
The biggest issue is not inhibiting navigation in low water conditions, natural materials and construction methods. You can pick up a permit from the DNR office off Clairemont. If you belong to a lake association or sporting organization it’s reasonably easy to get a permit, although rules have tightened (no more tire cribs like those in Wissota allowed – garbage in lake). Joe Kurz at Chippewa DNR office would be an exellent source of info, Dan Koitch in Eau Claire WAS previously the gatekeeper for such permits, but roles have changed over the years so you’ll have to verify. The DNR promotes fish habitat improvement on lakes where it is required due to lack of natural habitat. It’s a big task to take on by yourself, having been involved with several projects myself.