I began by exploring letter box sizes. How big could I enlarge that 'S' and still get the side flange sections onto my 12" card stock? Once that was determined, I sized the other letters somewhat smaller, and different from each other. I modified the upper right "arm" of the K to be shorter. I cut only the front side interior accent shapes using various prints, with all boxes themselves cut from black textured card stock.
Here is a closeup of the 3d ghost, and the miniature witch's hat.
And a closeup of how the non-dimensional spider and web were trimmed and attached across the largest 'O'.
Finally, a closeup of the 3d pumpkin and bat.
One suggested improvement to my experiment: since size changes affect the depth of the boxes, rotary-trim flanges to uniform size to match the shortest width before assembly begins.
Another trick: because rounded letters will fall over if not propped or anchored, I made a base of 1/4" thick black foam core and glued the letters to each other and to the base. Black wire placecard holders help the ghost and bat to "float". I used Distress Ink to shade paper edges.
Here are the Silhouette designs I used:
From Snapdragon Snippets - 3d s, p, o, k & y letter boxes, 3d bat, 3d ghost, 3d witch hat. From Pebbles In My Pockets - scalloped pumpkin. From Lori Lynn Whitlock - 8 fall leaves. From Silhouette unattributed designs - corner spider web & Halloween spider.
If you would like more information about my re-sizing of the various designs, email me (Jodi) with that request: hearthsewnpatterns(at)yahoo(dot)com .