If you want to avoid same-day bookings for only Booking.com reservations, you have two options that you can do on your Booking.com Extranet portal:
Option 1 via the EXTRANET CALENDAR:
This is highly recommended before connecting the property to Hostaway and via the Extranet Calendar.
You'll need to follow this guide from Booking.com.
On your Extranet Calendar, you'll be able to edit the Minimum Advance Reservation under specific Rate Plans and set in your desired number of days before the guest checks in.
Option 2 using RATE PLANS:
Under Rate Plans, you can change the Bookable time on your Booking.com Extranet to "Set number of days before check-in" to 1 day and click on Save.
If you haven't connected yet to Hostaway, please set your Bookable time before connecting and mapping the room to Hostaway.
If you've already connected and mapped to Hostaway, and wish to adjust the Bookable time, you can do so in the Rate Plans and then unmap and remap the room to apply the changes.