In a large bowl combine the dry ingredients: flour, salt, cream of tartar and pumpkin pie spice. Mix to combine using the spoon.
In a measuring cup, combine the 1 cup of boiling water, several drops of orange food colouring and oil. Add the remaining 1/2 cup of boiling water separately later as needed.
Add the boiling water mixture to the flour mixture a small amount at a time and mix until you have reached the desired consistency. If you are using a stand mixer, add the water as the mixer is turning.
Add the rest of the boiling water as needed until your dough is soft and not sticky (ie. It should not be sticking to your hands). If you add too much water it will be come sticky. If that happens, not to worry, simply add a pinch of flour and continue to mix until it is no longer sticky.
Add additional drops orange food colouring, if desired.
If kneading by hand, let the mixture cool before you pick it up and knead it. Wear gloves to prevent food coloring staining your hands. Continue kneading until it is smooth and no longer sticking to your counter.
If using a stand mixer let it continue to mix on high until it starts to form a dough ball and all the ingredients have been picked up from the sides.
Knead, knead, knead. Knead it until all its smooth, squishy and soft! The key to soft playdough is to continue kneading the ingredients together.