I breed in a 1g regular (15 x 15 x 25cm), 1g shallow (30 x 30 x 10cm), up to 50g (120 x 40 x 40 cm) - ALL depending on the male I'm breeding. I would use 1g for small young males and troubled males (less active). I use bigger tanks for regular healthy males that could literally swim around non stop all day and for half giants (I use 3-50g for half giants).
The depth also depends on the health. But usually I breed in regular depth ( as deep as I usually keep the tank). Sometimes bigger tanks are only filled half way. I've also bred in 2" water in the 1g shallow, 3-4" water in my 7g round tub..... all works.
So yes, your plan would work. IMO you don't need a divider but it won't hurt using them either. Without dividers may take longer but definitely safer for female since she has more space to avoid the male.
Do you Breed in 20 gal? Rather than a 10? I Have an empty 30 gal for a growout, Could I possibly spawn in there? My idea would be to fill up the tank only a few inches and use a home made divider to keep the pair in a section, so they don't lose each other, and once I take the male out, remove the divider.