Welcome to the site! Other than using OTAs you definitely want to focus your efforts on marketing your hostel for direct bookings. This can include:
Content marketing with SEO
Social Media Marketing with trackable promo codes
Affiliate Marketing with bloggers/vloggers/
Relationships with other hostels (who can refer business to you)
Can you please let me know the name of your hostel, website and social media channels and I'll try to provide some additional insights.