Build Service

public sealed class BuildService : IBuildService, IBindableAs

This class allows players to build buildings for their base.

You can use it directly from code. For example, here you can see, how to enable build mode on B key press with specific building selected.

public class ExampleBuilding : IUpdateSystem
{
  [Inject] UnitData buildingToCreate; // this requires some custom data from you, will not work directly as here
  [Inject] BuildService buildService;

  public void Update()
  {
    if (Input.GetKeyDown(KeyCode.B))
      buildService.EnableBuildMode(buildingToCreate);
  }
}