You may need to use a third pillow if you are making a bed for a large dog. You will probably need to sew by hand to avoid jamming the pillow into your sewing machine. Depending on the strength of your sewing, you may want to sew the pillows together on top where they meet in little valleys. This will help the pillows stay together and also create a more consistent shape. It helps to measure the pillows with a tape measure or yardstick and then transfer the necessary dimensions to a piece of fabric before cutting. Make sure to account for the height of the pillows by adding about four to six inches of extra fabric to each side of the cutout.  You can also lay the fabric over the pillows and mark where the fabric meets the pillow edges using a pen. Alternately, you can use old curtains instead of purchasing new fabric to save money and recycle your old things. Drape one piece over the pillow and place the other piece underneath the pillow. Make sure that the edges of the fabric match up. You can either fold as you sew or pre-pin all four sides of the bed before sewing using safety pins or sewing pins. Make sure to leave one side open in order to stuff the pillows inside. Make sure that the bed is evenly stuffed corner to corner. Snip any loose threads.  If you are seasoned at sewing, consider attaching a zipper to the fourth side of the bed. This makes it easier to wash the covering without having to wash the pillows as well. The bed can sit alone on the floor of your home, or you can place the bed in an adequately shaped box or basket for extra support and a more polished look. If using a box or basket, you can also sew strips of fabric onto the side of the bed to act as ties. You can then tie the pieces of fabric to the box or basket to prevent the bed from sliding.

TL;DR in Chinese:
拿两个大枕头，把它们重叠大约10-15厘米。 在枕头的重叠部分沿着边缘缝合线把它们缝在一起。 沿着第二道边缘缝合线再缝一次（如果有必要的话，缝第三次）。 选一块面料，切成足够包裹枕头的两部分。 用剪刀把面料剪开。 在缝纫之前把每块面料的边缘向内折，这样边缘就比较光滑圆润。 把床的三个边用缝纫机或者手工缝起来。 三边缝好之后，把枕头塞进去。 把剩下的一边也缝好。