I have a young C. sasanqua 'Cleopatra' start (got it last fall from the PHS plant divide here in Philly) in a small container (8" for now). Camellias in general are slow growing and upright, but I believe the sasanquas are a bit more open habit than japonicas. Does yours have a single main step with branches or multiple branches? I can see a multibranch form perhaps splaying open if there are young branches in heavy bloom but the branches should toughen over time and I expect they can be tied at the base to encourage an upright form.

Also, I would recommend not potting it up too much. One to two sizes above whatever it is in right now should be sufficient as these shrubs/trees can get root rot with too much container volume, since they tend to have mostly surface roots..

Jenny is right that you should grow your plant in containers that increase in size increments slowly. You don't want your plant to be sitting in a large pile of stagnant soil.

Sasanquas are commonly sold and grown attached to a trellis. However, they do beautifully if trained to be a tree form, as well. You would accomplish this by carefully removing the lower branches as the shrub develops and matures.

Janice, there's no "should" about trellises. The growth habits of sasanquas differ greatly with variety -- there are taller upright ones, bushy ones, and ones with low arching habits (such as a showa-no-sakae). If you took one of the latter to trellis, you'd be fighting its natural tendency. Ideally, if you wanted one to screen a balcony, you'd pick one with a more upright habit. If you have a tag that came with yours, it would help to determine how to treat it. Not that you couldn't trellis (or maybe espalier) a lower one, but it won't give you the privacy you might expect from a taller variety.

Some C sasanqua are bushy, upright grower, and some, low spreader. It is such a good habby plant that you can observe the plant to shape it accordingly by pruning or with stalk.

Best of all you may form it into a Bonsai. Bonsai size can be nimi, small, medium and large. It will take some sun. Keep the potting mix moist but never keep it too wet continuously.