[Nickp]

Have you considered a router with an edge guide, freehand, 1/2" down spiral bit...? Add a long piece of wood on the edge guide so you can route straight past the edge of the board...

Nibble away at it until you hit the desired depth...cut a line with a knife so you don't get tear out at the board end of the tenon...

Then flip it over and repeat. When done with the faces, chisel the edges to your dimension...

Start nibbling at the end of the board and work your way in so the router always has support...complete the cut to depth then move in some more til you get to your shoulder line...

I've also used a radial arm saw to nibble then dress it with a block plane and chisel...if you don't have a shoulder plane or router plane...

 

[Nickp]

I hadn't even thought about using a edge guide. Would that be with a plunge router? Plunging 1/4" and working to the end of the board. Then readjusting the fence in? The board is 7" wide. How long of a guide would you suggest? thanks

You want to start at the edge of the board to depth then move inward, again to depth, then inward, etc... This will keep the router supported until you come to the shoulder line. The longer piece of wood attached to the edge guide will allow the cut to start and end cleanly (square). The extra piece of wood should be long enough to allow the router to start and end squarely...probably long enough to allow about 6" on each end plus the base width of the router. That should be enough.

Whether you use a plunge or fixed is up to you...I would think both would be comfortable but I prefer a fixed so I don't jockey the router too much when starting and stopping.

As you can see from Tom's and Herb's responses there are various ways to use a router to do this...

 

[Nickp]

I like all those suggestions but I want to add the old school in case you are interested. Hand saws, chisels, planes. If only a couple of joints there is no time involved to make jigs and I like Japanese pull saws they cut clean and fast. It really doesn't take as long as some might think and it's relaxing. Don't get me wrong I like my routers also !

Then I think you have it...handsaw(pull saw), chisel, router plane (see Lee Valley or DIY - Youtube). Quite a few videos for a DIY router plane...

 

[Nickp]

...should you wish to use a Router Plane for the tenon, see Paul Sellers demonstrating his technique for making a tenon with a router plane and chisel and handsaw...there are other videos demonstrating this and other techniques...

Just in case anybody tells you it can't be done...