Voxel provides utility classes to arrange fields in a 12 column grid. You can apply a class to a field in the field options area

vx-1-1 // 100%
vx-1-2 // 50%
vx-1-3 // 33.3%
vx-1-4 // 25%
vx-1-6 // 16.6%
vx-2-3 // 66.6% 
vx-3-4 // 75%

If you need to, you can expand and create more classes with custom CSS, for example

.vx-5-12 {
  grid-column:  auto / span 5; 
}