It wasn’t too bad when I did mine, just a little tedious. You basically start by running the lace around the perimeter with the ends intersecting at the toe. Then pull slack to create the loops in the lace where you will then thread the ends through like regular laces. A paper clip is useful for pushing the lace around the perimeter and hooking it to create loops.
If one wants to do it efficiently get a lacing needle. Makes it much easier.
Start at the heal, lace both sides to the toes. Work from the toes back using the lace as the loops. Unlace one shoe at a time, so to use the other as a reference.