Siman 508
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א אֵין מְלַבְּנִים אֶת הָאֲבָנִים לִצְלוֹת אוֹ לֶאֱפוֹת עֲלֵיהֶם, מִפְּנֵי שֶׁמְּחַסְמָן; וְאֵין שׁוֹבְרִין אֶת הַחֶרֶס, וְאֵין חוֹתְכִין אֶת הַנְּיָר לִצְלוֹת עֲלֵיהֶם, וְאֵין פּוֹצְעִין אֶת הַקָּנֶה לַעֲשׂוֹתוֹ כְּמוֹ שִׁפּוּד לִצְלוֹת בּוֹ.
1 Things forbidden on Yom Tov for preparing roasted food. Containing 2 paragraph): We do not heat stones to roast or bake upon them, because this hardens them. We do not break earthenware, and we do not cut paper to roast upon them. And we do not split a reed to make it like a spit for roasting.
ב פּוֹצְעִים אֱגוֹזִים בְּמַטְלִית, וְלֹא חַיְישִׁינָן שֶׁמָּא תִּקָּרַע.
2 One may crack nuts with a cloth, and we are not concerned that it might tear.