bound-in supplement
Refers to a booklet, poster, or other insert that is physically bound into a book or magazine, not simply inserted loosely.
This magazine comes with a bound-in supplement in the form of a small booklet.
付録 is a general supplement or appendix, which may be bound in or loose. 綴じ込み付録 specifically means it is bound into the publication.
Standard kanji spelling using 綴じ込み (bound in) and 付録 (supplement).
Mixed kana-kanji spelling; 綴じ is replaced by hiragana とじ.
Mixed kana-kanji spelling; 綴じ込み is fully in hiragana.
Compound of 綴じ込み (とじこみ, 'binding in') and 付録 (ふろく, 'supplement').