I am still exploring the topic of riffle stacks. I came across this one in Ed Marlo’s “The Cardist,” Vol. 4. It builds the stack at the bottom of the deck during the shuffles as opposed to building the stack at the top of the deck. The problem with many of the riffle stack techniques that build at the top is that unless you are super-humanly good you will end up slowing down the shuffle as you near the top of the riffle so you can insure that you have the correct number of cards controlled by your thumbs. This change of speed occurs at the point in the shuffle where other players attention is the sharpest.
Not to mention how difficult it is to accomplish. As Marlo says:
JEAN HUGARD in one of his card books has described run-ups
The Cardist, Vol 4
from the top of the deck, in which it is necessary to hold
back a certain number of cards with each thumb in making the
riffle shuffle, at the finish of the riffle…I found this
very difficult of accomplishment at that time with any speed
or regularity in the riffle…FRANKLY, I STILL DO years later,
But by building from the bottom you reverse all of that. You start slow and then end up fast. You also can pre-count the cards, as you will see. The downside is that you need to use a crimped card so you can cut the stack from the bottom to the top.
Ok, at this point I am going to assume that the fifth card from the bottom is crimped, and that the aces are on top of the deck. Start by double cutting the aces to the bottom.
Now split the deck for your first riffle, but use your thumbs to riffle off four cards from the top half as you split the deck, and keep the break above those four cards.
Assuming a five handed game, your left hand drops three cards (Aces) and your right hand drops the four cards on those, then continue with riffling the left until you pass the crimped card. On this first shuffle that will be right away. Then finish the shuffle riffling both hands.
Now repeat that twice more, taking a four card break at the bottom of the right hand portion, but dropping one less card on each of the next two shuffles. So on the second shuffle drop two cards (Aces) with the left thumb, then drop the four cards, then continue riffling the left hand cards until you are pass the crimped card. The crimped card will be ten cards up from where you dropped the four. Once past, finish the shuffle.
On the third shuffle, get the four card break with the right thumb, drop the last single ace with the left thumb, drop the four cards with the right thumb. Riffle with the left past the crimped card (15 cards), then finish the shuffle.
Note that by cutting light on the right hand portion it makes the shuffle easier as you have more cards in the left. This gives you the ability to riffle past the crimped card and finish the shuffle with the right and left portions ending up even at the top.
Now all you need to do is cut to the crimped card, taking it to the bottom.
Additional thoughts.
You can get the fifth card crimped by simply crimping the bottom card and then beginning with a riffle shuffle to add four cards below it, while keeping the four aces on top. Then double cut the aces to the bottom.
Here is a video of a practice session: