A few of the stronger off site authority processes I use to build up a site are:
1) Take advantage of Press Releases - get a few of them over a period of time and link to your root page. You can use different inner page targeted KWs if you want but use the root page as the target in your PR.
2) High Metrics Web 2.0s - If you can find them, and you should be able to, add a fair amount of content to them and link to inner pages using those.
3) Parasite Pages - You'll find that some do not give you a do follow link but that is not the point of a parasite page when you are
using them for SEO. There are many that will give you authority links that are pretty strong for an authority backlink profile.
4) Private Blog Network Sites - We talk about PBNs here as a way to rank sites and they are a great tool for that. But many do not talk about using them as I do for an authority site for a long term benefit. You do not need a lot of these but get a handful of domains with good metrics, turn them into 25 - 35 page sites, and link only to your one authority site from them.