Yes of course, but if it's something you definitely want to book, we recommend the earlier the better to avoid disappointment in case of availability issues - we only get a certain allocation of rooms at each hotel.
Unlike many other travel companies, we don't enforce a single supplement.
All prices are based on sharing a twin room with someone of the same gender. Most of our Flashpackers find sharing a room great fun and end up becoming really good friends with their roomie. However, if you value your space, we get that and can arrange a single supplement.
As we use small boutique hotels we only have a few single supplements available so be sure to book early.
This article might help: Sharing a room - my advice to other Flashpackers