Hi Phil,
I think the solution you need is our Grid. This uses shortcodes, but nothing stops you from adding your own div with class or ID to customize the look and feel of it.
Additionally, you can nest one grid within another grid element. This would allow you to have, for example, three boxes across, and the right-most one, could have two vertically stacked boxes as in the example.
Please see
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and this wonderful documentation tells you all the tips and secrets to achieve your goal.
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Let us know if this helps.