public SliceDefinition()

//var voxelLayer = ... ;
//Must be on the QueuedTask.Run()

if (voxelLayer.Visualization != VoxelVisualization.Volume)
    voxelLayer.SetVisualization(VoxelVisualization.Volume);
voxelLayer.SetSliceContainerExpanded(true);
voxelLayer.SetSliceContainerVisibility(true);

//To stop the Voxel Exploration Dockpane activating use:
voxelLayer.AutoShowExploreDockPane = false;
//This is useful if u have your own dockpane currently activated...

//At 2.x - var volumeSize = voxelLayer.GetVolumeSize();

//Use the SelectedVariableProfile to get the slices currently in the TOC
//via its associated volume
var volume = voxelLayer.SelectedVariableProfile.Volume;
var volumeSize = volume.GetVolumeSize();

//Orientation 90 degrees (West), Tilt 0.0 (vertical)
//Convert to a normal
var normal = voxelLayer.GetNormal(90, 0.0);

//Create the slice at the voxel mid-point. VoxelPosition
//is specified in voxel-space coordinates

//At 2.x - 
//voxelLayer.CreateSlice(new SliceDefinition()
//{
//    Name = "Middle Slice",
//    VoxelPosition = new Coordinate3D(volume.Item1 / 2, volume.Item2 / 2, volume.Item3 / 2),
//    Normal = normal,
//    IsVisible = true
//});

//Create the slice on the respective volume
volume.CreateSlice(new SliceDefinition()
{
    Name = "Middle Slice",
    VoxelPosition = new Coordinate3D(volumeSize.X / 2, volumeSize.Y / 2, volumeSize.Z / 2),
    Normal = normal,
    IsVisible = true
});

//reset if needed...
voxelLayer.AutoShowExploreDockPane = true;