For pcbs with a lot of Swiss cheese like that it can be helpful to put the keycaps you need for the layout you want in order to identify which slots to use.
Thankfully the practice 65 doesn’t appear to be too open in terms of layout options. Looks like the main one will be the bottom row - where you’ll have to choose between the two layout options hilighted in blue:
e.g. If you want to use the 6.25u layout you’d be using the leftmost socket for lctrl and then evenly space out the other two based on a 1.25u key. The spacebar would go in the left option out of the 2 spacebar sockets so it’s centered, and then it’s 2 more 1.25u keys.