@baukepost Whilst I’m not a very experienced modeler I’ll certainly give this a shot.
First get a plane and a cylinder with 6 sides. Use a Boolean – Difference on the plane to cut a hole in the middle with the cylinder.

Once you do that, simply connect the verticies up.

After that, using the knife tool, cut squares into each corner of the plane.

Next, delete (not dissolve) the edge within the face, fill the four verticies and then move them as close together with Gx2. Do this for each corner.

After that feel free to use an modifiers like subsurf, solidify, array or mirror, though I find with an array you need to be very consistent with how tight the corner faces are.

One thing I didn’t show and just realised is you probably should connect each corner as to not have N-Gons.

EDIT: Just realised someone else responded with a much better way. Well I’ll keep this up regardless, and good luck with your modeling!