By slot? Grid 2 can do this with a custom grid addon if you do something like name your characters a specific way alphabetically.

If you prefer these are the steps:

Install Grid 2.
Make a folder in the _retail_/Interface/AddOns called 'Grid2MyLayout'

Add two files in this location, with the following content:

Filename: Grid2MyLayout.toc

## Interface: 80000
## Title: Grid2MyLayout
## Notes: My Custom Layout(s) for Grid2.
## Author: MadMilitia
## Version: v80000-1.0.0


## Dependencies: Grid2
Grid2MyLayout.lua
Filename: Grid2MyLayout.lua

Grid2Layout:AddLayout("2 Box", {
meta = {
raid25 = true,
raid15 = true,
raid10 = true,
raid = true,
party = true,
arena = true,
},
defaults = {
showSolo = true,
showPlayer = true,
sortMethod = "NAME",
unitsPerColumn = 2,
maxColumns = 2,
allowVehicleTarget = true,
},
[1] = {
nameList="characterName, characterName, characterName",
}
})


Grid2Layout:AddLayout("5 Box", {
meta = {
raid25 = true,
raid15 = true,
raid10 = true,
raid = true,
party = true,
arena = true,
},
defaults = {
showSolo = true,
showPlayer = true,
sortMethod = "NAME",
unitsPerColumn = 5,
maxColumns = 5,
allowVehicleTarget = true,
},
[1] = {
nameList="characterName, characterName, characterName",
}
})


Grid2Layout:AddLayout("10 Box", {
meta = {
raid25 = true,
raid15 = true,
raid10 = true,
raid = true,
party = true,
arena = true,
},
defaults = {
showSolo = true,
showPlayer = true,
sortMethod = "NAME",
unitsPerColumn = 5,
maxColumns = 2,
allowVehicleTarget = true,
},
[1] = {
nameList="characterName, characterName, characterName",
},
[2] = {
nameList="characterName, characterName, characterName",
},
[3] = {
nameList="characterName, characterName, characterName",
},
[4] = {
nameList="characterName",
},
})


Those 3 settings do a single row for 2 box, sorted by name. A single row for 5 box sorted by name and a 1 x 3 x 3 = 10 set for raiding.

You can add multiple rows in Grid2, put specific characters in specific rows, then set the style to whatever you like in Grid2. Ezpz. Then select the appropriate layout in /Grid2 > Layouts > Select by group / solo setting and the item from the above list, aka "5 Box"

Your group will be loaded exactly how you have it named in the lua config. Of course remember to load the new addon along with Grid2 in WoW!