Word shelves are not a new idea, however, the ones available in stores have two problems:
1. Finding the exact word you want is almost impossible.
2. The exact size you want is never available.
Making your own is simple and I have reduced it to a small number of steps which should work for most applications.
A power mitre saw is a necessity for this project. Unless you are adept with hand tools, cutting the complex angles required by hand will present a real challenge. A power mitre saw makes it easy.

Step 1: Measure and Make Templates

I needed a narrow shelf to display travel souvenirs and memorabilia. To fit my wall it had to be 42 inches in height. The word TRAVEL was chosen for the display. Since it has six letters, each letter had to be 7 inches tall. (42/6=7)
I decided that 4 inches in width would give a pleasing proportion to the letters. I cut six pieces of heavy paper to that size, 7x4 inches making certain they were absolutely square, in fact I used a carpenter's square to achieve that.
I decided to use 1x3 number one grade pine for this project since it was my intention to paint it. If you decide to stain yours, I would recommend a better quality hardwood. The actual size of 1x3 is actually 3/4" x 2,1/2" so when you draw the letters on your paper, you can use the edge of the actual board to get the proper thickness, as in the centre illustration. Take care to be as accurate as possible as these will be your actual templates for cutting the wood. Letters like A and V must overlap as in the photo. Next get some scissors and cut out your templates.

Step 2: Decide on Your Design

Lay the letters on a flat surface and arrange them in a design. The beauty of this method is that you can change them around until you find a pattern that looks good. When happy, tape them together and hold them against the wall the shelf will be displayed on. Keep tweaking the design until you are satisfied. Before you proceed to the wood stage, measure each part of every letter and total it up to determine how much wood you will need.

Step 3: Cut Wood and Make Sub-Assemblies

Cut all the straight parts, that is, the ones without angles first. Measure the pieces, or cut the letters apart and just transfer the sizes directly to the wood. This is the easiest step. Next, transfer the size of the angled prices to the wood. You will find that all the low angles are the same. In my case, they were 22.5 degrees and my mitre saw had a setting for that. Next, carefully cut the steep angles, as in my A and V. Notice that I was able to combine the T and R into one piece and the A and V as well. This saved some difficult joinery. Of course, once the pieces are cut they will have to be sanded carefully. Next, decide how you will join the pieces together. I used wood glue and a brad nailer to put together 3 sub- assemblies, TR, AV, and EL.

Step 4: Complicated Joins

In order to join the bottom of the R to the top of the A, strength was a major concern. I used 1/4" dowel, simply drilling two 1/4" straight holes into the bottom of the T. If you have dowel points, just insert them into the holes and align the A with the T. The points will mark where to drill. Otherwise, cut two equal pieces of dowel, mark the ends with paint and align them. Drill straight holes at the paint dots. Use glue liberally on the mating surfaces and in the holes, insert the dowels and press the pieces together. Use the same method to join the V and E. Let the glue dry overnight.

Step 5: Final Sanding

Take time to clean off any exposed glue, sand with medium sandpaper to smooth the joins between each letter, then use successively finer sandpaper to get a nice smooth finish. Clean off any dust with a tack cloth.

Step 6: Mounting Holes

Turn the shelf over and drill a number of holes to ensure secure mounting, especially if your shelf is heavy or will be supporting a large load. In my case, I drilled 6 shallow 1/4" holes. Mark the hole locations with a light pencil mark at top and bottom of each location. Hold the shelf against the wall in the exact location where it will be mounted and transfer the pencilled locations to the wall. Drill the wall at the exact centre of each of these locations and install plastic anchors and screws. Make sure the heads of the screws fit into the holes you drilled in the back of the shelf.

Step 7: Test Fit and Finishing

Try the shelf on the wall and make sure it will support the load. Also check to see if it is level. If not, adjust till you are satisfied. Finish the shelf with the appropriate paint or stain. In my case I used one coat of Hi- Hide primer and two coats of Low Gloss trim enamel. I sanded lightly after the first two coats. Now is also a good time to touch up the wall, in case you marked it up test fitting the shelf. When the shelf is completely dry, install it permanently and load it up with all the stuff you built it for.
While every shelf will be different, I hope my method works for you.