Hopefully someone can help me with this. I notched the 2 bricks that go on each side of the form for the chimney. Do i notch the next ones back? It seems like there will be a gap bigger than the form. I will attach pics.
Thank you 
Now that I am out of the 95° heat, I am thinking the gap is for tge mortar, oh well, at least I got to cool down!
Since this is the chimney… and since this area sustains MASSIVE amounts of heat, I’m going to lean on the side of caution and say yes, you should notch those connecting fire brick and mortar those into place as tightly as possible to the connecting fire brick.
High temp mortar could be used to fill that larger-than-normal space… but it would be better to use the fire brick as it is better suited to handle such high temps year after year.
