Once all the legs have been fit to the top slab of the bench, we can fit the stretchers. These will not only tie the bottom structure together more rigidly, but also provide a place for a shelf. The first part of this is to rip out some stock for the stretchers.
Once that’s done and the resultant pieces trued up, we cut tenons into the ends of the stretchers.
Then we have to create mortices in the legs to join the stretchers to. When all of those are fit, we need to undertake a step that might not be readily apparent. Those stretchers are going to meet in the middle of the leg. Therefore, they must be mitred, or they’ll bind up. So, all of the tenons get mitred before we go on. Do test fit these, because you don’t want them to bind up when you’re trying to glue this whole mess together.