Attic Windows is a wonderful framing block, to showcase photos, pieces of special fabric, or other blocks.
Traditionally, Attic Windows was made with the dreaded "Y seam," i.e., a seam that requires a quilter to make a diagonal seam fit in the corner of two sides at right angles. I can do Y-seams, I have done Y-seams, but I avoid them when I can! (Tip, if you do a y-seam: mark the 1/4" seams carefully, and sew only to the point where 2 seams meet/intersect. That's the only way to set the y-seam accurately.)
But for our Attic Windows we're going to use squares and our old friend the HST, or Half-Square Triangle. (For instructions for making HSTs, see BOW #1)
For a 12" block you will need:
(4) 3-1/2" squares light (or a photo, or fussy-cut piece of a favorite fabric)
(4) 3-1/2" HSTs Dark1
(4) 3-1/" HSTs Dark 2
The two dark fabrics are going to form the frame of the window, with a shadowed side.
Arrange the pieces as shown:
You could rearrange the dark pieces to put the shadow to the right, instead of at the bottom, if you like. You get to choose where the light is coming from. :-)
Here's an example of an Attic Windows adaptation to form a frame around blocks in a sampler quilt. In this case I used rectangles in place of the dark squares, but still used HSTs for the corners.
(You may see some familiar blocks in this quilt....)
And here's an Attic Windows that is really a sort of double window (and I remember that I did Y-seam construction on this one, which has been in my collection for about 30 years):