Late reply, but the way that OTS slots work is planned out very far in advance. Currently active duty applying to the November 2019 active duty board and if I get accepted I will not attend until 2021. They have all the slots filled on the active duty side a year to a year and a half in advance. They also have multiple boards. So for FY2020 there will be two active duty boards and two civilian boards. The later boards are notorious for being cancelled though, so it gets tough.
On a side note, if you are applying non-rated then the selection rates are very low based on how many people apply. So unless you stand out above everyone else it could take a few times to get accepted. Hope this helps.