That's not a wall ride....
...this is a wall ride lol!!!
The angle isn't really critical, it's more the shape leading into it in our experience
That one in the pic above is made of 8x4 sheets of 18mm ply leaning longways (the long edge vertically) against a wall...with 8x4 sheets of hardboard laid (with the short edge vertically) forming the curves on and off...and it worked well.
My advise with wall rides would be to make it as wide/tall/long as you can...otherwise it's a bit of a non entity of a track feature...ones that form hairpins are over so quickly it almost isn't really a feature! Your on and off it in prob not much more than a second...prob less in reality...so go as big/wide as you can!
And make sure it's high enough that you can get a full track width above the apex...otherwise it can be a bit of an obstacle in race conditions.
Practical limitations obviously dictate how big you can go...but aim big to begin with would be my advice!