One thing you have to do for some special units is create a custom base.  There are a few ways to go about doing this.  I started trying to layer 2mm black sheet styrene and cutting a circular hole with a 1" flat bit; that didn't work out too well (next time I am going to try a 1" round hollow bit).  With time running out I had to make a base quick and settled on the following method.

Step 1: Sheet Styrene

I used 2mm black sheet styrene.  Scored with an exacto knife using a square as a guide, and then broke by applying pressure over a table's edge.

Step 2: Rare Earth Magnets

GW suggests using Blu-Tac to hold models in place but that can become messy over time.  While this is cost effective I prefer a more secure hold so I went with Rare Earth Magnets.  You can get these at Michael's for $5 for a pack of 6 (or off the Internet for significantly cheaper).  I used the 13mm (or quarter inch) magnets though smaller would work better.  You'll want to carefully position the magnets on the base and affix with super glue - remember to account for the slot which splits the base on the bottom - you cannot center the model on the magnets easily.

Step 3: Elmer's Glue, Sand, and Spray Primer

I applied Elmer's Glue (not thinned with water) and dumped sand over the surface.  I also applied a few loose rocks.  When this dried I sprayed the entire base with spray primer.  I avoid using Gesso or paint primer because it weakens the bond of the Elmer's Glue creating a big mess.

Step 4: Paint and Seal

Paint the base with your browns, drybrush, and then seal.  I like Dullcote, its strong and will not gloss or satin your finish.

Step 5: Flock

I flocked my base using GW's Citadel Grass (the light happy summer green) and Silflor Buffalo grass (spring green).  The Buffalo grass is expensive at $25 for a box, but it will last you a long time and it looks very nice.  (Buffalo grass comes pre-clumped.)

Step 6: Galvanized Washers

Zinc washers #6 size.  I glue these onto the bottom of my bases; #6 size is small enough to fit on either side of the slot under the base.  Be mindful of your magnet placement when super gluing these onto your model.

Done!

Certainly does not take long to have a very simple but decent looking base.  I would say that overall these flat bases are easier to complete than the GW War of the Ring molded bases because gluing the sand onto those bases can create problems getting your models in and out.  If you do use the molded bases, make sure you have a test model to try each slot before the sand dries in place and you prime the base.