As we've previously written about, this summer, the LSAC quietly ended its partnership with Khan Academy and all free official LSAT prep materials are now available only at lawhub.lsac.org. Four official PrepTests are now offered, but these PrepTests do not offer explanations. So, it might be a good idea to save them for closer to your test day as a measure of how you're performing, instead of as a tool for learning and improving.
However, another resource, the official "Drill Sets", includes an extra 168 practice problems and the vast majority of them have never been included in prior LSAT prep materials. This article is based on our YouTube playlist on Lawhub's logical reasoning drill set #1.