Place pork and slow cooker sauce in a slow cooker. Cover and cook on low for 7 hours.
Remove pork and shred using two forks. Return pork to the slow cooker and toss in the sauce. Set aside.
Place water, butter and rice in a small sauce pot, bring to a boil. Once boiling, reduce to low, cover and cook until all the liquid is absorbed.
Once rice is cooked, add the chopped pineapple and green onion and mix to combine.
Heat enough oil in a large skillet to coat the bottom of the pan over medium-high.
Once hot, add 1 of the flour tortillas and cook for about 1 minute on each side until browned and crispy. Transfer to a paper towel lined plate to drain and repeat with remaining tortillas.
Brush the top of a tortilla with BBQ sauce, spread rice on top, then pork, top with another tortilla and repeat the process to make stacks of 2 or 3.