1 English cucumber, cut into 1/4-inch-thick slices
Set the oven to 350 degrees Fahrenheit and foil a baking sheet.
Scoop out the seeds after cutting the squash in half lengthwise. After liberally salting the flesh, slather it with 1/4 cup of the barbecue sauce. Place the squash flesh-side down on the baking sheet that has been prepped, and roast for 45 to 1 hour, or until it is soft and the strands can be easily parted with a fork. Allow them to cool on the baking pan for a short while.
In the meantime, in a small pot, combine the maple syrup, tomato paste, 2/3 cup of the vinegar, remaining 1/2 cup barbecue sauce, a dash of salt, and 1 cup of water. Bring to a boil, then lower the heat to a simmer, and cook for 15 to 20 minutes, or until thickened. Stay warm.
In a medium bowl, combine the remaining 2 tablespoons of vinegar with the mayonnaise, cabbage, and onion. Use salt to season.
Squash strands can be separated using a fork (keep them in the skins). The squash strands should be evenly coated after you divide 1 1/4 cups of the sauce between the two halves. Use salt to season.
About three-quarters of the way through, split the buns open. Slices of cucumber are distributed throughout the buns. Give them a hearty helping of the squash, then sprinkle some slaw on top. Extra sauce should be served on the side.