Fairly easy after ranking up cards to at least copper. It can be done with stone cards but why punish yourself?
The only card that does not need to be upgraded at all for this is the Echoes of the Future spell.
This time around you will also want to add in another Spawner for this difficulty. Preferably either Skelton Archers (skeleton archers stack bleeding effects when they attack) or Stone Weavers. As you cast spells and summon units you will be able to spawn more things as time goes on. Hitting the space bar will let you quickly swap between the front lines and the spawn area.
At the beginning of the match you will want to place a Cauldron Spawner and as soon as they spawn in the match keep spawning Stone Weavers on top of the cauldron. If you have acquired Crystal Chanters summon just one as it will be enough. Save a little mana here and there for heals as needed for your cauldron. Once you have crushed the first tower heal up your cauldron and start to spawn a few groups of Skeleton Archers as the second and third towers have considerably more units protecting the tower. Do not go over board with the archers as siege damage from either the stone weavers or ballista do significantly more damage. Around the third tower or after feel free to use Echoes and spawn in as many units as you can and you should win around the two or three minute mark.