Ok, so I know the model will be mostly stock, now I've got to get the base ready.
I started by trying to figure out what the ‘footprint' of this kit will be, that is, how much space does it need to be properly displayed.
I set the model on a piece of thick paper, and added about an inch to either side for terrain and incidentals. (In hindsight, I should have added the legs to the piece before deciding how big it's base should be. Ah well, if there's not enough room, I can always make another. )
Once I had a rough idea how much space it would take up, I cut a piece of the approximate size from the paper. Seems about right.
Then I used that guide to make a mock up of the base from paper and tape. I decided to make the base ¾ of an inch thick, for no other reason than it looked about right.
Next, using the pieces of my mock up as a template, I scribed and cut pieces of 2mm sheet styrene, and used those pieces to assemble the base. I end up having a box shaped display, w/ a 2mm tray in it to contain whatever I use for ground work (celluclay or mold-a-scene most likely). Notice I added a ¾ inch border on the front. This is a place for the model's title, and maybe the scale.
I'm not done yet though. The base is too lightweight, and I'll want to drill into it so I can mount the model on a brass rod, so...
I flip the base over, and run superglue into the corners. I then swept the scriber shavings and the plastic dust from sanding the pieces into the tray, shaking it around so that it sticks to the glue. Waste not, want not.
For years now, whenever I finish a kit I've saved the excess sprues. I chop them up into manageable pieces and store them in a bag.
Here's why; First I take the extra sprue and shake it into the tray, using only enough to fill in almost to the brim, but not quite.
Then I break out the casting resin. This particular batch is getting old, and is only suitable to the purpose I intend for it.
I mix up the last of it, and pour it into the tray over the sprue bits.
As it hardens, it expands slightly, and it gets very hot. The old plastic bits act as heat sinks, absorbing some of the heat and keeping the tray from melting. The plastic also takes up space (volume) and therefore I can use less resin.
When it hardens, it turns white. It didn't quite fill up the base, but that ‘s the last of it. It works for what I needed it to; I makes the base solid gives it some weight, and also gives me a foundation to drill into.
After filling the outer seams w/ superglue and sanding everything flush, I check to see if I still like the size. It's all good, so now it's ready to be drilled and painted.