In The Thrifty Quilter, I show one way to make half-square triangles (HST’s). I’m often asked if these units have to be made using this method when making the blocks in the book. No, they don’t. I went with that particular method because it was easy to use for any size HST needed in the book. To be honest, it isn’t even my favored method.
For those who don’t have the book, I’ll explain the method used there, first:

Step one: Take two 2.5″ squares and place them right-sides together. Draw a diagonal line on the back side of the lighter square.

Step three: Open the HST unit and press. I almost always press my seams open, but you can press to the darker triangle if you prefer.
That’s it…three easy steps. Of course, there is a down-side to this method, in that you use two squares to make one HST, and you wind up throwing away a pretty good-sized piece of each square. Few of us would cry over the tiny “waste” triangles from a 2.5″ HST, and I have discovered that if you save the waste triangles from 3.5″ squares, you can actually still make a 2.5″ HST from them. The leftovers from a 4.5″ HST would give you enough to make a 3.5″ HST.
Now, here is the method I use most often. Take the finished size of HST you need and add 1″. Since the HST’s I’m using in this block are 2″ finished, I need 3″ squares to start. Of course, I have a Thrifty Quilter bin full of 3.5″ squares, so I’ll just use those.

Step one: Place a dark and light square right-sides-together, draw a diagonal line on the back of the lighter square and sew 1/4″ on each side of the line. Cut the triangles apart on the drawn line.

Step two: Press open. You need a ruler with a 45degree diagonal line that goes into the corner. Lay this diagonal line on the seam, making sure the portion of your square under the ruler is larger than 2.5″ (or the desired size of the HST you’re making). Trim the right and top sides.

Step three: Flip the HST around and lay the ruler down again with the diagonal line on the seam. This time, the sides you just cut should line up with the 2.5″ vertical and horizontal lines on the ruler. Again, trim the right and top sides.
There are a couple of advantages to using this method. First, you get two HST’s from two squares with less waste. Second, the HST’s are exactly the size you need. The bonus: no dog ears to trim!
So, let’s fill a scrap basket with HST’s, shall we?
To make this 10″ block, you will need:
Nine 2.5″ HSTs that are half print and half white
Six 2.5″ HSTs that are two prints
One 4.5″ HSTs that is half brown and half white
Two 2.5″ brown squares
Two 2.5″ x 4.5″ white rectangles
Sew the pieces into units as shown above. You can see this leaves you with four square units that are sewn together first. The sew the strips of white/print HSTs to the right side and top to complete your Overflowing Scrap Basket block.
Make two of these blocks, and over the Labor Day weekend, I’ll give you a tablerunner pattern to make with them!