11. Here it comes the interesting part. Select the same polygons as me, then in the edit window, right click on the selected polygons and choose Break. This will detach the selected polygons from the those unselected.
12. Having those poligons still selected, move them in the texturing square. Then choose “vertex” as selection and pick a vertex from the edges of that shape. You will see that another vertex will be highlighted with a blue color. This means that the selected vertex should be welded to that one
13. Like you already noticed, we need to flip our shape and place near the other one. Then we will weld the vertices
14. Now select 2 vertices that should be welded and then right click > Weld selected. In the same time, look in the viewport to see that the green line will disappear. This happens because those 2 parts are welded and now is a single shape.
15. Continue to weld the vertices until both parts are welded. And I hope that you remember when I sayd that all squares should be the same, well, here is how we will solve this. If you look at the top of the head, those square have a strage shape, there are no squares anymore. Just play with the vertices in the “Edit UVW’s” window. What did I do to unwrap the head is this : I have aligned the vertical vertices and then I’ve moved them to left/right . Like this I have obtained equal squares every where. If you want to do the same thing, select each row of vertices, align them and if necessary, move them to left or right. Check the following images, it will help :