So here it is, my Air Castle Block Tutorial.
To make one 10" finished block cut:
one 5" square in your secondary fabric for the small triangles (dots)
two 4 1/2" squares in your primary fabric for the large triangles (peach print)
one 4" square for the center square (blue floral)
one 5" square from your background fabric (cream)
four 4" squares from your background fabric (cream)
The basis of this block is the Boston Block which is basically a double HST. We are going to make 4 of these at once.
Make your first set of HSTs by drawing a diagonal line on your 5" background square.
Place the 5" squares right sides together and sew 1/4" from both sides of line.
Cut on the line and press towards the printed fabric.
Trim squares to 4 1/2".
Repeat the process using the two 4 1/2" squares of your primary fabric and your HSTs. Make sure that you align the drawn diagonal line opposite the sewn seam.
Sew 1/4" on each side of drawn line and cut on the line.
Press towards the primary fabric to reduce bulk.
Trim squares to 4".
Note, this method produces two opposing sets of Boston blocks which is what we need for this block. This method will not work for a block that needs four matched Boston blocks like a pinwheel. Trust me on this!
Sew together your rows as shown.
Press towards the 4" square so that your seams will oppose when you sew your rows together.