First a confession. You know how sometimes when you make one thing simpler, you may two things more complicated? Well it looks like I might have done that. I love this slotted stem for the ease of gluing sides and for the nice curved cut water you can make with little effort. However, it turns out that the chine logs and the gunwales now have to have a compound angle cut on them to fit the stem. So here's a choice point for you. You can use a normal internal stem sawn at 27 degrees, and skip this compound angle stuff or you can do what I did. Get out your bevel gauge.
Unclamp half the chine log, apply glue and re-clamp and hammer the nails home. Hold a sledge or heavy weight behind where you hammer as a "bucking iron." It absorbs the impact of your hammer and makes it all much easier.
Do the same to the other side.
The chines are planed level with a hand or power plane. A straight edge helps. A long board with course sand paper on one end will work also. Resting one end on the other chine keeps the sanding end level.