public class VoxelVolume 

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

//At 2.x - var slices = voxelLayer.GetSlices();

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

//Do something... e.g. make them visible
foreach (var slice in slices)
{
    slice.IsVisible = true;
    //at 2.x - voxelLayer.UpdateSlice(slice);
    volume.UpdateSlice(slice);
}

//expand the slice container and make sure container visibility is true
voxelLayer.SetSliceContainerExpanded(true);
voxelLayer.SetSliceContainerVisibility(true);

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

//At 2.x -
//var slice = voxelLayer.GetSlices().FirstOrDefault();
//var slice2 = voxelLayer.GetSlices().First(s => s.Id == my_slice_id);

//Use the SelectedVariableProfile to get the slices currently in the TOC
//via its associated volume
var volume = voxelLayer.SelectedVariableProfile.Volume;
var slice = volume.GetSlices().FirstOrDefault();
var slice2 = volume.GetSlices().First(s => s.Id == my_slice_id);