Automotive?
You still get spikes from turn-off. If you build the bridge tight together and load it up with bypass caps, you can use the body diodes to clamp it for the most part. Relaxed turn-off time helps, and is the main difference between doing full PWM with it, versus limited switching.
To keep it slow, you may have to add your own Miller capacitors -- transistors these days have so little feedback capacitance, they switch quickly even with very slow gate drive. An R+C from D to G will do.
I recommend using several transistors in parallel for each leg of the H bridge, to widen the current path. Keep layout tight, to minimize path length. Route on top for the most part, reserving the bottom for ground plane, for bypass caps. The wide paths also allow you to put caps between transistors, keeping loop inductance low.
The alternative to capacitors is TVS diodes, which could be rated for 15 or 18V nominal, which would clamp around 30V (check the datasheet; note and compare test current). This accounts for not just back EMF, but supply inductance -- whatever the cable length from the battery (or other source) is, it has stray inductance and will store a significant amount of energy at these currents.
And yes, that's multiple TVSs, interspersed just as the capacitors would be. The switching current can be absorbed by direct clamping, or bypassing. Bypassing of course being the lower loss option, making PWM an option, even if you don't need it right now.
Exactly how many TVSs and transistors to use, what ratings, and what switching speed, all depends on the layout. I would do a tentative first layout, estimate its performance, then update parts selection, and so on. Then make the prototype, and verify those predictions, or correct them if in error.
The transistors can do the clamping directly, but I do not recommend it. MOSFET avalanche should be a one-time thing, at worst. Repetitive avalanche ratings, if given at all, are low; and as far as I know, incremental damage is always done, no matter the current or pulse width. Relying on avalanche, puts a cycle limit on your device.
There were two threads in here recently (a few months ago), on basically exactly this subject, I don't remember the titles unfortunately; see if you can find them?
Tim