DIY cross-leg Garden Table & Bench
Fix the X legs to the braces
Align the bolt holes in the crosses with the pilot holes in the braces [b], insert
5/16" x 5" galvanized hex lag screws with washers into each hole and tighten them up.
That will pull everything in nice and tight and (if the cuts are square) should automatically make the legs 90° to the braces.
While tightening the bolts, ensure that the two table rails are on the same plane, and that the two bench rails are also on the same plane as one another. You may have to twist the frame slightly to achieve this.