First, I highly suggest you print out this pic that I created in EQ - the arrangement of the little HST's can be confusing! (HST's = half square triangles)
Now, you will need six 5'' charm squares for each block (the block will be 9 1/2'' after assembly with a finished size of 9'' in your quilt). 3 charms need to be the same print/color and 3 charms need to be the same solid.
Now, cut diagonally both ways to create 4 triangles on these squares
Then, take each triangle and open them up and press carefully to create 8 HST's.
Now comes the trimming! Square each little triangle up so they end up 2 3/4'' square.
refer to the picture you printed out. Notice that the 3 'inner' on each corner all point in the same direction. Dark toward the dark block, light toward the light block. The outer corners are the only one's that are rotated.
Sew the little HST's into pairs and then into the 4 patches. Then, sew the triangle patches to each solid charm and then the two pairs together.
and now you have your finished Hunter's Star block! You should be able to get 36 of these from 3 charm packs to create a 54x54'' quilt top with a 6x6 block layout. Or, add a 4th charm pack and border the 36 Hunter's Star blocks with the whole charm squares to create a 63x63'' quilt top like I did below. You will have leftovers for piecing a backing as well if you do it this way. If you wanted to use all 40 charms from each pack on the front, you could do a 5x8 block layout and end up with a 45''x72'' quilt top without the 4th charm pack. You could then add the 4th charm pack and bring that up to 54''x81'' which could be a single bed size or a nice size couch/lap quilt.