You need to start with to begin feeding both the male and female special diets for about 3 weeks ahead of time when the female starts to have a load of eggs and then the male needs to be moved to a specially prepared at least 10 gallon quarantine tank (shallow water, sponge filter -cycled through the Nitrogen cycle COMPLETELY with air valve to be able to control air flow so there is not so much disturbance in the water to disturb the bubble nest, lots of hiding places for female to hide when spawning is over as there will be a chance of fighting between the sexes and possible death of one or both if protection is not provided); 5 gallon cycled quarantine tank for female to be housed in after spawining to recover (not the same tank she came out of before spawning as she needs to be alone for a while to get her strength back); 55 gallon growth tank cycled for female betta fry when the sexes become obvious - also equipped with a completely cycled sponge filter and lots of hiding places; LOTS of small jars or containers for the male fry as they will need to be seperated as soon as you can tell their sex or they will kill each other. (as these will not be able to be heated or filtered be prepared to keep them in a well protected area away from drafts and direct sunlight. Keep in mind that they will all need to have their water changed every day (50%) the females tank and all of the jars and the water you replace needs to be of the correct temperature and treated with a good dechlor agent so you will need a good thermometer preferably one of the ones used to with glass tube - not digital. and a lot of dechlor agent - I would get a couple of pint containers to start with and a set of measuring spoons to be used for fish only if you do not already have one and a gallon plastic pitcher as things need to be MEASURED with fry not guessed at. In each of the larger tanks you will need to have dependable heaters like Vist-therm Stealth that give a good dependable steady temperature and a tank thermometer for each one (the glass tube type - they are more accurate) You are also going to need a Master Test Kit if you do not already have one as the water needs to be checked at least every other day in each of the tanks to make sure that the parameters are as perfect as possible as the fins and bodies of the fish will be deformed if they are not.
Bettas are very difficult fish to breed and it is not a task that many are anxious to take on. They need almost 24 hour supervision before the spawning takes place to make sure that they do not injure or kill each other. They cannot just be put together and allowed to breed. There is a process that HAS to be followed and that is why the breeding is generally left to the professionals who have not only the equipment, but a staff who provide 24 hour supervision of the process to prevent the loss of an expensive breeding pair. If your fish do not happen to be an introduced breeding pair, there is always the chance that breeding just is not going to happen as they do not always take to each other and will not spawn no matter what you do.
Who told you no gravel? But if nothing else, tie some small baggies about the bottom stems of the plants or such with bags of gravel and then the gravel is about the end of the plant without being spread all over the bottom of the tank attach it with string wound about and tied or thread or some sort of fish line. Just do not leave LONG tails so the cannot get wrapped up in it. I have seen fish keepers who do have their whole tanks done this way and it make a pretty tank.
The male is generally right there and pretty attentive and does not let that happen. They are not dropping that fast and furiously and he is a very attentive daddy. Besides there are always a few that are not meant to make it. It would be very unusual for every egg to hatch and produce a new betta. If you saw pictures of the male attending the nest he is never usually more that a few centimeters away.