Century 21 Apex Property deals mostly with projects around Phnom Penh and other major cities in Cambodia, like Sihanoukville (aka Kompong Saom), Battambang or Siem Reap. Needless to say that large projects are for the moment highly concentrated in and around the capital. And contrary to belief, there are still (at the time of this article) plots of lands available in Phnom Penh. There are some empty lands, ready to be conquered, on the main city boulevard, especially the famous and beautiful Norodom Boulevard. Now, these plots are available, we did not say affordable. You would have to have very deep pockets to acquire one of them, as nothing would trade under $M10.
As for the rest of the counties, land is still widely available, and we would suggest to get in touch with one of our agents to find out more. And if you have a specific region in mind, know that Century 21 Cambodia is establishing one agency in all 23 provinces, through one of its franchisee (Zillion Holding).
Also, we recommend to visit the Zillion Homes, a web application that gathers updated listing of properties and land for sale