I first stripped off the minis from one of the sets of 3 temporary bases and remove the double-sided tape from those. That can be thrown away as it's useless now.
I used to go through a rather laborious process of gluing the minis to the bases with Aleene's Tacky glue and then carefully putting pre-mixed filler all over the base, waiting to dry and painting with the Burnt Umber Crafter's Acrylic, but I've found a much quicker and actually much cheaper way.
I use Brown Acrylic Frame Sealant from Screwfix. If you go down this route make sure you don't get Silicone as that won't take paint! I slavered a thin layer of this onto the base and it acts as all three of the stages above, glue, filler and paint! You do get a bit of shrinkage as it dries, but not enough to cause a problem.
So first into the brown goo was the rear rank, mounted officer and drummer. You'll notice I've had to move the officer from his planned central position to the edge because he just would not fit in the middle.
Anyway, after pushing the models in with my sculpting tool I reversed the tool and pushed the goo around to merge in with the bases. Goo is the correct term with this stuff, it's sticky, soft and, if you're not careful, can get everywhere. It sticks to fingers and tools. Luckily it also is relatively easy to wipe off and is water-based. Still you don't want to get it on the models if you can help it hence using one end of the tool for pushing the models around and the other for the goo itself, trying to keep the former end as clean as possible.
After getting those in the right place I applied the front rank and standard bearer and then after more adjustment the skirmishers.
Then a small rectangle was scraped off one of the rear corners. That will be where I put the unit identifying marks.
You will also notice the bit I have hanging off the front. The base is quite messy whilst this is wet and that can be cut off a lot more easily when it's dried.
So I did this with all three bases and then left them overnight to dry.
Tonight I finished them off. First I tidied up the edges with a sharp knife.
Then a heavy dry brush with Beasty Brown and also painting the edge and the unit marking area with the same.
Then a lighter dry brush with Pale Sand mixed 50/50 with the Beasty Brown.
The last dry brush is just Pale Sand on it's own.
The dry brushing will mess up the edges and unit marking area, so that needs tidying back up with Beasty Brown. This also is a second coat which is often needed around the edges anyway.
The various markings are then added. I outlined them with black, which is the colour I have chosen to help distinguish the nation of this army. French I did with blue, British with red and Russian with green.
The markings themselves are II for the Corps number and the small 1 next to it is to signify the 1st Brigade of that in case I need that detail. The 6 is the Elan of the unit and a small S for the Skirmish Trait. I have various letter codes for the different traits. Most are just the obvious initials. All except Shock and Steady, which become A (for attack) and D (for defence) as otherwise there are too many S's.
There is also a white mark on the front middle. I don't bother with arc markings on the base as I use an arc of fire template for that.
After this the static grass is applied. These are home-made self adhesive tufts of 2mm spring meadow static grass. I use something like this to make those in bulk from time-to-time. (Edit: See here for how I make them.) They are just pulled off the backing paper with tweezers and put where needed. They can even be moved if I'm not happy with them. Even months after being stuck in place.
And here they are all done. Just a quick spray with matt varnish and they're ready for battle.
In the comments I was asked what sculpting tool I used. It's actually a wax carving tool that I obtained years ago. I found them still available on ebay. Anyway here's a photo along with some more casualty markers that I am making right now using much the same techniques as above.