Use fabric weights with bulky fabrics
While most fabrics can be easily pinned to the sewing pattern on top, some thick bulky fabrics cannot be pinned in a conventional fashion. In this case not only is it helpful to use sharp rotary cutters in the pattern cutting process, you will also have to stabilize the pattern and fabric layers underneath with fabric weights.
Once the pattern is carefully aligned on grain as noted by the pattern's grainline, weight should be applied closer to pattern's corner and edges in order to keep them as flat and smooth as possible in the cutting process. The garment pieces are then cut very carefully, making sure not to shift the fabric layers and pattern in the process. This technique is similar to tracing a stencil where the fabric cut needs to be the exact replica of the paper pattern.
You do not need to use store0-bought fabric weights but rather anything that is weighty enough to stabilize and flatten your patterns in the cutting process. Heavy stone coasters or even bookend will work as long as they do not cause any staining damage to the fabric or paper pattern.