Help Replicating a filter

My buddy has a cold plunge and this filter started cracking. After looking at it you can tell it's definitely 3d printed (and well)

On the left you can see my first attempt. I just cut rectangular holes in CAD and it's pretty close but not pretty. Printed in PETG on a K1 Max

Is there a way to do this in the slicer instead? I played around with 0 walls and different infill types but that didn't work out