Flying wings can be designed the same way you design an airplane that has a horizontal stab and elevator.

I have taken a standard airplane and chopped off the horizontal stab and elevator, moved the CG forward to 15% of MAC and then had a great flying model. If you want dihedral, put it in. Do whatever you want. Just remember to move the CG forward.

Build a free flight profile model glider of your proposed design. Launch it using a catapult. That model will show you where the CG should be. Attached photo of some cat launched styrofoam free flight glider.

Rudders work fine on a flying wing. The attached model can do knife edge flight the length of our flying field.

If you want a trainer with rudder and elevator, do a flying wing glider as shown in the attached photo.

Build all models in foam.

My background is 30 years of designing building and flying Flying Wings made from Styrofoam.

Attached is my latest project. Vulcan Bomber with a 36" wingspan.