Well, you can do everything you wish with your threads – this here is just a suggestion for a very fast and easy technique how you can make two fast strings for the fastening/closing.
Count your threads – you have 2 colors on each side with 2 threads for each color – the most easy and fast braiding needs 3 threads. That means, if you count every color as just one string (if you want to keep the sides balanced and the threads homogeneous instead of braiding with 1-1-2 strings) then you need one pair extra on every side.
For this purpose you need to see how long the threads are which you have – you should have at least 20-30 cm – the shortest thread should be longer than that. For this two extra threads just take about the double length of the shortest thread of one side (you can add a little extra) and cut this two threads with this length.
As you can see on the picture above I just inserted this two extra threads through this last stitches I did at the border.
…and so I got two extra threads for each side – enough for the next step – the braiding and completely without mixing any colors (in one “thread”). 🙂
Start with one side – you can braid until you reach the end of your shortest thread on this side – here you can make a knot.
As soon as you finished the first string, start braiding the other one. You can stop as soon as you are as long as the other braid or when you reach the end of your shortest thread…