If the pack takes an hour to interpret, it isn't a management report. A structure that survives contact with a board.
Most management packs fail for the same reason: they report the accounts rather than the business. Structure the pack around decisions and the drivers behind them.
Three pages is usually enough: performance against plan, cash and runway, and the two or three drivers moving the result. Everything else is an appendix.
Consistency compounds. The same format, delivered on the same date each month, turns reporting into a management habit rather than an event.