Always use stabilizer when embroidering.
For large designs split into sections, the stabilizer must be attached to the fabric, for example, by using iron-on stabilizer, self-adhesive stabilizer or spray adhesive. Use stabilizer appropriate for the fabric.
In addition, be sure to use stabilizer that is strong enough and large enough for the entire embroidering area. You may need to attach two layers if thin stabilizer is used.
See more information about stabilizer, "Step 4 Attaching stabilizer to the fabric".