So, i played minecraft with my selfmade modpack but i couldn't find any pebbles or make flint shards. I used creative mode and JEI but the items are not there

Given the total lack of any versions or other relevant information provided, I shall explain for the latest (1.16) version:

• Pebbles do not spawn in newer versions (1.16) yet due to world gen not being implemented.
• Flint shards are made by Knapping.