Heat a grill pan or grill. Slice the halloumi into 1/4" thick slices and toss with the olive oil, cumin, and coriander. Rinse the scallions and toss with the olive oil. Grill the halloumi and scallions until charred, 2 to 3 minutes per side (depending on the heat strength.)
Remove the halloumi and scallions from the grill and let cool slightly. Chop the halloumi into smaller strips and mince the scallions. Dice the avocado into small cubes and place in a bowl along with the chopped scallions, lemon juice, and salt. Toss to combine.
Assemble the tacos with roughly 1/4 of the cheese, 1/4 of the avocado mixture, cilantro (or micro greens), and a splash of hot sauce as desired.