Another thing to bear in mind, is that presumably your half-bridge drivers are connected by wires to something off-board. And so the wires become receiving antennas as well as transmitters. Same with the ground return wires to the external devices. These can all pick up spikes large enough to glitch logic, when propagated through ground planes under logic ICs.
If you want a truly reliable device, it's best to have two separate ground-power plane pairs. One for all the internal logic. This doesn't connect to anything off-board apart from the power supply (and that via RF filters.) And as others have mentioned, no slots, islands, current loops, etc, or you're making a transmitter.
All external I/O goes on another section of the board, with its own planes. You can still run this from the same power supply, but the decoupling should be much lower pass, and inductors, etc designed to take the expected currents. Decouple ALL the supply and ground rails, equally. The only connection between the logic and I/O plane areas should be at the one point the rails are joined via low pass filters.
The idea is that you are expecting the I/O circuit rails to be bouncing up and down quite a bit (relative to the logic planes), due to external noise pickup, drive current loops, etc.
Then for logic signals between the two areas, you have to provide some electrically isolated paths. There are many ways. You can use an optocoupler per signal, or some form of serial bus with only two or three optos, or signal transformer coupling, or whatever. Method depends on your required bandwidth.
It's best if there is no 'state memory' at all in the entire semi-floating I/O section. Since that whole plane is expected to be quite noisy, and the purpose of the exercise was to avoid logic glitches having any effect on operation.
This does mean that the serial I/O bus decoupling method is risky, since that implies state memory.