Do not know about stablizder.
For what it is worth. It is an accepted quilting standard that all seams in a quilt are 1/4". read your pattern to see if your blocks or parts of blocks are finished or unfinished size. Finished size includes seam allowances, Unfinished means you have to add 1/4" seam allowances to every piece regardless of size or shape.
Suggestion do not do final trimming on any finished blocks until all are made. There may be a differences in finished sizes for what ever reason. Trim all to smallest size. Many quilters make certain blocks a little larger for this reason.
Good Luck and remember to have fun.
Do not know this particular pattern, but sometimes pattern authors assume we know everything. Also I have found in some patterns directions are written very confusingly. If you can not solve this, perhaps a visit to the local quilt store with pattern is in order. They may be able to decifer this for you.