My experience has been that it grows fairly fast from seed. You'd probably do just as well to sow it directly.

A warning, though -- a mulched bed isn't really ideal for sideoats grama. It's a grass that likes hot and dry. To the west of here it's often found at the top of slopes where the soil is lean and rain drains away from it. Also it doesn't keep a tight bunch form, but tends to spread somewhat irregularly and also seed around quite a bit.

I think it's best in a densely planted, non-mulched bed, surrounded by other grasses and perennials that can compete with it, like it is here on the High Line:

http://www.thehighline.org/blog/2014/08/19/plant-of-the-week-sideoats-grama

The flowering stems are fantastic spraying out among the other plants. This might be just what you're looking for, but if you're thinking about a grass that stays in a nice round form, I'd keep looking.

Also my experience with both sideoats grama and blue grama is that in my yard they grow taller than advertised. My sideoats stems are generally in the 2.5 - 3" range, same for (non-cultivar) blue grama. I think my location isn't ideal for either of them, probably too rich and moist for them to keep a good form. We get around 40" of precip here annually. I know texasranger2 has some that keep a tighter, more upright form, but it's hotter where she is and also she's added a good deal of sand to her yard. It could also be different genetics.

Again, I really do like this grass, but it definitely has more of a loose textural appeal rather than a structural one for me.

We get a lot of rain but the condition is medium to dry. The beds have a southern exposure and get full sun + wind from traffic because it's on a roadside. I should probably call it an improperly mulched bed because the mulch is only 1-2" deep and underplanted. It requires a lot of weeding.

My intention is to go more in the direction of that highline planting you linked. I've been reading Planting in a Post-Wild World and other books with these types of designs.

I currently have phlox subulata growing in a 2-3ft area adjacent to the retaining wall, but it's planted too sparsely and too far from the retaining wall to fully cover the ground. My plan was to divide some of the phlox and transplant them all closer to the retaining wall, then plant the side oats roughly in a line behind it spaced 24-30" apart leaving space between some of the clumps for other plants like purple coneflower and lance leaf coreopsis. Theres already baptisia australis and tiny, baby leadplant roughly in a line behind where I'd put the line of grass. I have plant ideas to fill in the rest of the space too. Here, pictures are worth a thousand words in this case (please excuse the leaves and dying plants lol):