Try this site for plans. www.zyworld.com/TheWick Otherwise let your raw fingers tour some books at the library or your favorite home cheapo.
You are going to have to custom fit any plan to fit your kitchen any way. Basically frame up the base in a box with 2by4s at a comfortable height for you which will probably be around 18" or use your own chair heights. when building the base for height, allow for the plywood seat base with however much foam (3 or 4" or so) padding you will add. Use 2by4 bracing every 16" under the seat. Finished depth of the seat will probably be around 18" after allowing for the back which will have a plywood base with your foam (2" or so)and upholstry which is stapled to the plywood. You may want a 1by4 frame behind the seat back for putting your arms up or setting a cup their and if so then adjust the base depth accordingly.
Build it with whatever plywood matches your trim and finish it and then use removable upholstered cushions is a way to do it. Start carrying your tape measure when you go out to eat and measure the corner booths of the ones you like. They all start with a 2by4 frame. Sit in a chair you find comfortable to get your finish height and depth cause it depends upon how tall or short everyone is.