You say you know how to use all kinds of saws and you have several saws. You mentioned looking at the Rockler Template.
Do you have a router if you had a template? If you do have a router and bushings or collars make your own template. Make 1 pattern and shift it across the template material equally spacing as you go, cut, shift cut, shift. Then use the template to cut the mortises for the louvers.
If you don't have a router but have a table saw you can cut groves in a work piece to accept the louvers. Make a box joint type jig but make it on an angle. Cut your slots for the louvers then add strips to each side of the work piece to capture the louvers. then build the rest of the frame.
Keep your jigs because when you show your friends the grill you made they will want some made too.
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