Handworked thread loops have a nice discrete, lightweight finish and are great for delicate fabrics and areas where there is little stress placed on the closure. They can also be worked in a straight line to form an eye for a hook, or made longer to form a belt loop at a side seam, but I'll demonstrate the loop version here.
Thread your needle with an arm's length of thread and knot the ends together so it is doubled. Insert the needle a short distance from where you want the loop to be, exiting at one end of the loop:
Pull the thread to draw the knot between the layers, then take a couple of small stitches to secure the thread where it exits:
Insert the needle at the top end of the loop and exit at the bottom end - try to pass the thread through multiple thicknesses for extra strength, without catching the front layer so it remains invisible from the right side:
Do this 2-3 times to make a loop, stick the needle in the centre of the loop and wiggle it so all threads are the same length, and check that it fits your button. You can still tighten or loosen it at this stage:
If you are making a bar for a hook, make this 'loop' so it lies flat on the cloth with a slight gap for the hook to pass through.
Now we blanket stitch around the loop to make it firmer - bring the needle up through the loop:
Then pass it through the loop that you have just formed:
And slowly draw up the thread being careful not to twist or knot it:
Tighten the stitch and at the same time slide it to the very start of your loop:
And keep repeating....
Keep the blanket stitches as close together as possible without overlapping. If your thread gets twisty, drop the needle and let it swing - it will spin and untwist the thread itself.
Keep going until you get to The End:
Zig-zag the needle and thread a few times through the seam allowance between the layers to finish off, exit again at a distance from the loop, then clip the thread close to the cloth. If your loop is the correct length, the edges at the front should butt together when buttoned like so - no overlapping or gaps!