Several ways you could applique them by hand. You could do the traditional hand applique where the stitches do not show. You could do a blanket stitch around them in a blending or contrasting color. You could also do a running stitch to hold them in place. I have seen them done all those different ways. There are probably even more...like you could use some embroidery stitch besides the blanket stitch if you wanted. How wonderful for you to have the blocks!