Adding / joining limbs is very simple.
Sorry that I don't have a diagram to follow, but with reference to teddy...hope this helps...
Set pieces out i.e....leg / body / leg.... placing and mark with pin or pen.
Use dental floss if possible. A long needle...a sharp doll needle if possible. (The teddies are so small that I managed with a long sewing needle )...YEP...I made another one today !
Start on inside of leg,( leaving a long spare of thread / flossing hanging, for knotting later) and pass needle to outside of leg; then go back to inside of leg, a 'milliwotsit' from where needle went in.
Push needle right thru body ( using your pin/ pen marks as a guide).
Continue thru inside of second leg...to outside... then the tiny 'milliwotsit' stitch back to inside of leg.
You should now be back to where the long spare thread/flossing is hanging.
Pull both threads /dental floss until limbs feel firm and then tie a firm knot.
I find the most difficult aspect of making matching twos of anything is the need to get them the same size ! So I worked the legs / arms /ears together.