Louver fence. How do I attach them?

[GabeBli]

I am going to build a new fence for a basement entrance (see attached image for reference). I'm considering 28 x 45 fence slats horizontally. But how do I attach them?

The current fence is attached to metal posts which are in OK condition. But I don't really see how I can attach a bunch of narrow fence slats to them.

Does anyone have a clever solution in stock?

 

[Matti_75]

Screw a slat standing in the post to which you attach your horizontal slats.

 

[GabeBli]

Screw a vertical strip onto the post that you attach your horizontal strips to.

Sounds reasonable.
What's the best way to screw it on?
Drill into the post and attach the strip with a nut?

 

[Matti_75]

With carriage bolt in the holes you already have in the post